diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index acb9c860e..2fcb44477 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1168,7 +1168,6 @@ set (PCH_SOURCES
 	p_udmf.cpp
 	p_usdf.cpp
 	p_user.cpp
-	p_writemap.cpp
 	p_xlat.cpp
 	parsecontext.cpp
 	po_man.cpp
diff --git a/src/actor.h b/src/actor.h
index 439ae2644..d4f5f27c5 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -779,14 +779,7 @@ public:
 	// set translation
 	void SetTranslation(FName trname);
 
-	double GetBobOffset(double ticfrac = 0) const
-	{
-		if (!(flags2 & MF2_FLOATBOB))
-		{
-			return 0;
-		}
-		return BobSin(FloatBobPhase + level.maptime + ticfrac);
-	}
+	double GetBobOffset(double ticfrac = 0) const;
 
 	// Enter the crash state
 	void Crash();
diff --git a/src/am_map.cpp b/src/am_map.cpp
index 9f68f944e..09ca93b96 100644
--- a/src/am_map.cpp
+++ b/src/am_map.cpp
@@ -70,6 +70,7 @@
 #include "po_man.h"
 #include "a_keys.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 
 //=============================================================================
@@ -601,23 +602,21 @@ CUSTOM_CVAR (Int, am_showalllines, -1, 0)	// This is a cheat so don't save it.
 {
 	int flagged = 0;
 	int total = 0;
-	if (self > 0 && numlines > 0)
+	if (self > 0 && level.lines.Size() > 0)
 	{
-		for(int i=0;i<numlines;i++)
+		for(auto &line : level.lines)
 		{
-			line_t *line = &lines[i];
-
 			// disregard intra-sector lines
-			if (line->frontsector == line->backsector) continue;	
+			if (line.frontsector == line.backsector) continue;	
 
 			// disregard control sectors for deep water
-			if (line->frontsector->e->FakeFloor.Sectors.Size() > 0) continue;	
+			if (line.frontsector->e->FakeFloor.Sectors.Size() > 0) continue;	
 
 			// disregard control sectors for 3D-floors
-			if (line->frontsector->e->XFloor.attached.Size() > 0) continue;	
+			if (line.frontsector->e->XFloor.attached.Size() > 0) continue;	
 
 			total++;
-			if (line->flags & ML_DONTDRAW) flagged++;
+			if (line.flags & ML_DONTDRAW) flagged++;
 		}
 		am_showallenabled =  (flagged * 100 / total >= self);
 	}
@@ -1030,17 +1029,17 @@ static void AM_findMinMaxBoundaries ()
 	min_x = min_y = FLT_MAX;
 	max_x = max_y = FIXED_MIN;
   
-	for (int i = 0; i < numvertexes; i++)
+	for (auto &vert : level.vertexes)
 	{
-		if (vertexes[i].fX() < min_x)
-			min_x = vertexes[i].fX();
-		else if (vertexes[i].fX() > max_x)
-			max_x = vertexes[i].fX();
+		if (vert.fX() < min_x)
+			min_x = vert.fX();
+		else if (vert.fX() > max_x)
+			max_x = vert.fX();
     
-		if (vertexes[i].fY() < min_y)
-			min_y = vertexes[i].fY();
-		else if (vertexes[i].fY() > max_y)
-			max_y = vertexes[i].fY();
+		if (vert.fY() < min_y)
+			min_y = vert.fY();
+		else if (vert.fY() > max_y)
+			max_y = vert.fY();
 	}
   
 	max_w = max_x - min_x;
@@ -2382,7 +2381,6 @@ bool AM_isLockBoundary (line_t &line, int *lockptr = NULL)
 
 void AM_drawWalls (bool allmap)
 {
-	int i;
 	static mline_t l;
 	int lock, color;
 
@@ -2393,18 +2391,18 @@ void AM_drawWalls (bool allmap)
 		if (p == MapPortalGroup) continue;
 
 
-		for (i = 0; i < numlines; i++)
+		for (auto &line : level.lines)
 		{
 			int pg;
 			
-			if (lines[i].sidedef[0]->Flags & WALLF_POLYOBJ)
+			if (line.sidedef[0]->Flags & WALLF_POLYOBJ)
 			{
 				// For polyobjects we must test the surrounding sector to get the proper group.
-				pg = P_PointInSector(lines[i].v1->fX() + lines[i].Delta().X / 2, lines[i].v1->fY() + lines[i].Delta().Y / 2)->PortalGroup;
+				pg = P_PointInSector(line.v1->fX() + line.Delta().X / 2, line.v1->fY() + line.Delta().Y / 2)->PortalGroup;
 			}
 			else
 			{
-				pg = lines[i].frontsector->PortalGroup;
+				pg = line.frontsector->PortalGroup;
 			}
 			DVector2 offset;
 			bool portalmode = numportalgroups > 0 &&  pg != MapPortalGroup;
@@ -2418,10 +2416,10 @@ void AM_drawWalls (bool allmap)
 			}
 			else continue;
 
-			l.a.x = (lines[i].v1->fX() + offset.X);
-			l.a.y = (lines[i].v1->fY() + offset.Y);
-			l.b.x = (lines[i].v2->fX() + offset.X);
-			l.b.y = (lines[i].v2->fY() + offset.Y);
+			l.a.x = (line.v1->fX() + offset.X);
+			l.a.y = (line.v1->fY() + offset.Y);
+			l.b.x = (line.v2->fX() + offset.X);
+			l.b.y = (line.v2->fY() + offset.Y);
 
 			if (am_rotate == 1 || (am_rotate == 2 && viewactive))
 			{
@@ -2429,9 +2427,9 @@ void AM_drawWalls (bool allmap)
 				AM_rotatePoint(&l.b.x, &l.b.y);
 			}
 
-			if (am_cheat != 0 || (lines[i].flags & ML_MAPPED))
+			if (am_cheat != 0 || (line.flags & ML_MAPPED))
 			{
-				if ((lines[i].flags & ML_DONTDRAW) && (am_cheat == 0 || am_cheat >= 4))
+				if ((line.flags & ML_DONTDRAW) && (am_cheat == 0 || am_cheat >= 4))
 				{
 					if (!am_showallenabled || CheckCheatmode(false))
 					{
@@ -2443,27 +2441,27 @@ void AM_drawWalls (bool allmap)
 				{
 					AM_drawMline(&l, AMColors.PortalColor);
 				}
-				else if (AM_CheckSecret(&lines[i]))
+				else if (AM_CheckSecret(&line))
 				{
 					// map secret sectors like Boom
 					AM_drawMline(&l, AMColors.SecretSectorColor);
 				}
-				else if (lines[i].flags & ML_SECRET)
+				else if (line.flags & ML_SECRET)
 				{ // secret door
-					if (am_cheat != 0 && lines[i].backsector != NULL)
+					if (am_cheat != 0 && line.backsector != NULL)
 						AM_drawMline(&l, AMColors.SecretWallColor);
 					else
 						AM_drawMline(&l, AMColors.WallColor);
 				}
-				else if (AM_isTeleportBoundary(lines[i]) && AMColors.isValid(AMColors.IntraTeleportColor))
+				else if (AM_isTeleportBoundary(line) && AMColors.isValid(AMColors.IntraTeleportColor))
 				{ // intra-level teleporters
 					AM_drawMline(&l, AMColors.IntraTeleportColor);
 				}
-				else if (AM_isExitBoundary(lines[i]) && AMColors.isValid(AMColors.InterTeleportColor))
+				else if (AM_isExitBoundary(line) && AMColors.isValid(AMColors.InterTeleportColor))
 				{ // inter-level/game-ending teleporters
 					AM_drawMline(&l, AMColors.InterTeleportColor);
 				}
-				else if (AM_isLockBoundary(lines[i], &lock))
+				else if (AM_isLockBoundary(line, &lock))
 				{
 					if (AMColors.displayLocks)
 					{
@@ -2483,25 +2481,25 @@ void AM_drawWalls (bool allmap)
 				}
 				else if (am_showtriggerlines
 					&& AMColors.isValid(AMColors.SpecialWallColor)
-					&& AM_isTriggerBoundary(lines[i]))
+					&& AM_isTriggerBoundary(line))
 				{
 					AM_drawMline(&l, AMColors.SpecialWallColor);	// wall with special non-door action the player can do
 				}
-				else if (lines[i].backsector == NULL)
+				else if (line.backsector == NULL)
 				{
 					AM_drawMline(&l, AMColors.WallColor);	// one-sided wall
 				}
-				else if (lines[i].backsector->floorplane
-					!= lines[i].frontsector->floorplane)
+				else if (line.backsector->floorplane
+					!= line.frontsector->floorplane)
 				{
 					AM_drawMline(&l, AMColors.FDWallColor); // floor level change
 				}
-				else if (lines[i].backsector->ceilingplane
-					!= lines[i].frontsector->ceilingplane)
+				else if (line.backsector->ceilingplane
+					!= line.frontsector->ceilingplane)
 				{
 					AM_drawMline(&l, AMColors.CDWallColor); // ceiling level change
 				}
-				else if (AM_Check3DFloors(&lines[i]))
+				else if (AM_Check3DFloors(&line))
 				{
 					AM_drawMline(&l, AMColors.EFWallColor); // Extra floor border
 				}
@@ -2512,7 +2510,7 @@ void AM_drawWalls (bool allmap)
 			}
 			else if (allmap)
 			{
-				if ((lines[i].flags & ML_DONTDRAW) && (am_cheat == 0 || am_cheat >= 4))
+				if ((line.flags & ML_DONTDRAW) && (am_cheat == 0 || am_cheat >= 4))
 				{
 					if (!am_showallenabled || CheckCheatmode(false))
 					{
diff --git a/src/bbannouncer.cpp b/src/bbannouncer.cpp
index a19ba72f4..6fbf31479 100644
--- a/src/bbannouncer.cpp
+++ b/src/bbannouncer.cpp
@@ -49,6 +49,7 @@
 #include "d_player.h"
 #include "g_level.h"
 #include "doomstat.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/c_cmds.cpp b/src/c_cmds.cpp
index 2923a8ae8..be4944b8c 100644
--- a/src/c_cmds.cpp
+++ b/src/c_cmds.cpp
@@ -72,6 +72,7 @@
 #include "r_utility.h"
 #include "r_data/r_interpolate.h"
 #include "c_functions.h"
+#include "g_levellocals.h"
 
 extern FILE *Logfile;
 extern bool insave;
diff --git a/src/c_console.cpp b/src/c_console.cpp
index 0e9b94996..8bf7f4cd9 100644
--- a/src/c_console.cpp
+++ b/src/c_console.cpp
@@ -67,6 +67,7 @@
 #include "d_player.h"
 #include "gstrings.h"
 #include "c_consolebuffer.h"
+#include "g_levellocals.h"
 
 #include "gi.h"
 
diff --git a/src/compatibility.cpp b/src/compatibility.cpp
index 8f4472c85..0b27a1efa 100644
--- a/src/compatibility.cpp
+++ b/src/compatibility.cpp
@@ -52,6 +52,7 @@
 #include "p_tags.h"
 #include "r_state.h"
 #include "w_wad.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -475,9 +476,9 @@ void SetCompatibilityParams()
 			{
 				case CP_CLEARFLAGS:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						line_t *line = &lines[CompatParams[i+1]];
+						line_t *line = &level.lines[CompatParams[i+1]];
 						line->flags &= ~CompatParams[i+2];
 					}
 					i+=3;
@@ -485,9 +486,9 @@ void SetCompatibilityParams()
 				}
 				case CP_SETFLAGS:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						line_t *line = &lines[CompatParams[i+1]];
+						line_t *line = &level.lines[CompatParams[i+1]];
 						line->flags |= CompatParams[i+2];
 					}
 					i+=3;
@@ -495,9 +496,9 @@ void SetCompatibilityParams()
 				}
 				case CP_SETSPECIAL:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						line_t *line = &lines[CompatParams[i+1]];
+						line_t *line = &level.lines[CompatParams[i+1]];
 						line->special = CompatParams[i+2];
 						for(int ii=0;ii<5;ii++)
 						{
@@ -509,9 +510,9 @@ void SetCompatibilityParams()
 				}
 				case CP_CLEARSPECIAL:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						line_t *line = &lines[CompatParams[i+1]];
+						line_t *line = &level.lines[CompatParams[i+1]];
 						line->special = 0;
 						memset(line->args, 0, sizeof(line->args));
 					}
@@ -520,9 +521,9 @@ void SetCompatibilityParams()
 				}
 				case CP_SETACTIVATION:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						line_t *line = &lines[CompatParams[i+1]];
+						line_t *line = &level.lines[CompatParams[i+1]];
 						line->activation = CompatParams[i+2];
 					}
 					i += 3;
@@ -552,9 +553,9 @@ void SetCompatibilityParams()
 				}
 				case CP_SETWALLYSCALE:
 				{
-					if (CompatParams[i+1] < numlines)
+					if ((unsigned)CompatParams[i+1] < level.lines.Size())
 					{
-						side_t *side = lines[CompatParams[i+1]].sidedef[CompatParams[i+2]];
+						side_t *side = level.lines[CompatParams[i+1]].sidedef[CompatParams[i+2]];
 						if (side != NULL)
 						{
 							side->SetTextureYScale(CompatParams[i+3], CompatParams[i+4] / 65536.);
diff --git a/src/d_main.cpp b/src/d_main.cpp
index 1ea2d2707..2c6b1c9e9 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -109,6 +109,7 @@
 #include "p_local.h"
 #include "autosegs.h"
 #include "fragglescript/t_fs.h"
+#include "g_levellocals.h"
 
 EXTERN_CVAR(Bool, hud_althud)
 void DrawHUD();
diff --git a/src/d_net.cpp b/src/d_net.cpp
index 4bda25510..0ebb7de38 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -63,6 +63,7 @@
 #include "r_utility.h"
 #include "a_keys.h"
 #include "intermission/intermission.h"
+#include "g_levellocals.h"
 
 EXTERN_CVAR (Int, disableautosave)
 EXTERN_CVAR (Int, autosavecount)
diff --git a/src/decallib.cpp b/src/decallib.cpp
index 7bfdfc3e7..52a4eadf5 100644
--- a/src/decallib.cpp
+++ b/src/decallib.cpp
@@ -49,6 +49,7 @@
 #include "colormatcher.h"
 #include "b_bot.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 FDecalLib DecalLibrary;
 
diff --git a/src/dobject.cpp b/src/dobject.cpp
index c6e20be5e..b96cc5ff9 100644
--- a/src/dobject.cpp
+++ b/src/dobject.cpp
@@ -49,6 +49,7 @@
 #include "dsectoreffect.h"
 #include "serializer.h"
 #include "virtual.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/dobjgc.cpp b/src/dobjgc.cpp
index 11cfdc8c2..625f80678 100644
--- a/src/dobjgc.cpp
+++ b/src/dobjgc.cpp
@@ -77,6 +77,7 @@
 #include "r_utility.h"
 #include "menu/menu.h"
 #include "intermission/intermission.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -709,15 +710,15 @@ size_t DSectorMarker::PropagateMark()
 			moretodo = true;
 		}
 	}
-	if (!moretodo && sides != NULL)
+	if (!moretodo && level.sides.Size() > 0)
 	{
-		for (i = 0; i < SIDEDEFSTEPSIZE && SideNum + i < numsides; ++i)
+		for (i = 0; i < SIDEDEFSTEPSIZE && SideNum + i < (int)level.sides.Size(); ++i)
 		{
-			side_t *side = &sides[SideNum + i];
+			side_t *side = &level.sides[SideNum + i];
 			for(int j=0;j<3;j++) GC::Mark(side->textures[j].interpolation);
 		}
 		marked += i * sizeof(side_t);
-		if (SideNum + i < numsides)
+		if (SideNum + i < (int)level.sides.Size())
 		{
 			SideNum += i;
 			moretodo = true;
diff --git a/src/doomstat.cpp b/src/doomstat.cpp
index 87ca50a16..309398331 100644
--- a/src/doomstat.cpp
+++ b/src/doomstat.cpp
@@ -29,6 +29,7 @@
 #include "i_system.h"
 #include "g_level.h"
 #include "p_local.h"
+#include "g_levellocals.h"
 
 int SaveVersion;
 
diff --git a/src/edata.cpp b/src/edata.cpp
index 258c2a187..015be0bb1 100644
--- a/src/edata.cpp
+++ b/src/edata.cpp
@@ -49,6 +49,7 @@
 #include "v_palette.h"
 #include "p_acs.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 
 struct FEDOptions : public FOptionalMapinfoData
@@ -705,7 +706,7 @@ void ProcessEDLinedef(line_t *ld, int recordnum)
 	ld->flags = (ld->flags&~fmask) | eld->flags;
 	ld->setAlpha(eld->alpha);
 	memcpy(ld->args, eld->args, sizeof(ld->args));
-	tagManager.AddLineID(int(ld - lines), eld->tag);
+	tagManager.AddLineID(ld->Index(), eld->tag);
 }
 
 void ProcessEDSector(sector_t *sec, int recordnum)
@@ -760,12 +761,12 @@ void ProcessEDSectors()
 	auto numsectors = level.sectors.Size();
 	int *sectorrecord = new int[numsectors];
 	memset(sectorrecord, -1, numsectors * sizeof(int));
-	for (int i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		if (lines[i].special == Static_Init && lines[i].args[1] == Init_EDSector)
+		if (line.special == Static_Init && line.args[1] == Init_EDSector)
 		{
-			sectorrecord[lines[i].frontsector->Index()] = lines[i].args[0];
-			lines[i].special = 0;
+			sectorrecord[line.frontsector->Index()] = line.args[0];
+			line.special = 0;
 		}
 	}
 	for (unsigned i = 0; i < numsectors; i++)
diff --git a/src/fragglescript/t_cmd.cpp b/src/fragglescript/t_cmd.cpp
index 1434870d1..691740024 100644
--- a/src/fragglescript/t_cmd.cpp
+++ b/src/fragglescript/t_cmd.cpp
@@ -48,6 +48,7 @@
 #include "g_level.h"
 #include "r_renderer.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/fragglescript/t_func.cpp b/src/fragglescript/t_func.cpp
index 080adbd46..514d9aaea 100644
--- a/src/fragglescript/t_func.cpp
+++ b/src/fragglescript/t_func.cpp
@@ -71,6 +71,7 @@
 #include "r_utility.h"
 #include "a_ammo.h"
 #include "math/cmath.h"
+#include "g_levellocals.h"
 
 static FRandom pr_script("FScript");
 
@@ -2171,7 +2172,7 @@ void FParser::SF_SetLineBlocking(void)
 			int i;
 			while ((i = itr.Next()) >= 0)
 			{
-				lines[i].flags = (lines[i].flags & ~(ML_BLOCKING | ML_BLOCKEVERYTHING)) | blocking;
+				level.lines[i].flags = (level.lines[i].flags & ~(ML_BLOCKING | ML_BLOCKEVERYTHING)) | blocking;
 			}
 		}
 	}
@@ -2194,7 +2195,7 @@ void FParser::SF_SetLineMonsterBlocking(void)
 		int i;
 		while ((i = itr.Next()) >= 0)
 		{
-			lines[i].flags = (lines[i].flags & ~ML_BLOCKMONSTERS) | blocking;
+			level.lines[i].flags = (level.lines[i].flags & ~ML_BLOCKMONSTERS) | blocking;
 		}
 	}
 }
@@ -2251,11 +2252,11 @@ void FParser::SF_SetLineTexture(void)
 			while ((i = itr.Next()) >= 0)
 			{
 				// bad sidedef, Hexen just SEGV'd here!
-				if (lines[i].sidedef[side] != NULL)
+				if (level.lines[i].sidedef[side] != NULL)
 				{
 					if (position >= 0 && position <= 2)
 					{
-						lines[i].sidedef[side]->SetTexture(position, texturenum);
+						level.lines[i].sidedef[side]->SetTexture(position, texturenum);
 					}
 				}
 			}
@@ -2270,7 +2271,7 @@ void FParser::SF_SetLineTexture(void)
 			FLineIdIterator itr(tag);
 			while ((i = itr.Next()) >= 0)
 			{ 
-				side_t *sided = lines[i].sidedef[side];
+				side_t *sided = level.lines[i].sidedef[side];
 				if(sided != NULL)
 				{ 
 					if(sections & 1) sided->SetTexture(side_t::top, picnum);
@@ -3363,19 +3364,19 @@ void FParser::SF_ObjState()
 void FParser::SF_LineFlag()
 {
 	line_t*  line;
-	int      linenum;
+	unsigned linenum;
 	int      flagnum;
 	
 	if (CheckArgs(2))
 	{
 		linenum = intvalue(t_argv[0]);
-		if(linenum < 0 || linenum > numlines)
+		if(linenum >= level.lines.Size())
 		{
 			script_error("LineFlag: Invalid line number.\n");
 			return;
 		}
 		
-		line = lines + linenum;
+		line = &level.lines[linenum];
 		
 		flagnum = intvalue(t_argv[1]);
 		if(flagnum < 0 || (flagnum > 8 && flagnum!=15))
@@ -3987,9 +3988,9 @@ void FParser::SF_SetLineTrigger()
 			mld.special = spec;
 			mld.tag = tag;
 			mld.flags = 0;
-			int f = lines[i].flags;
-			P_TranslateLineDef(&lines[i], &mld);
-			lines[i].flags = (lines[i].flags & (ML_MONSTERSCANACTIVATE | ML_REPEAT_SPECIAL | ML_SPAC_MASK | ML_FIRSTSIDEONLY)) |
+			int f = level.lines[i].flags;
+			P_TranslateLineDef(&level.lines[i], &mld);
+			level.lines[i].flags = (level.lines[i].flags & (ML_MONSTERSCANACTIVATE | ML_REPEAT_SPECIAL | ML_SPAC_MASK | ML_FIRSTSIDEONLY)) |
 				(f & ~(ML_MONSTERSCANACTIVATE | ML_REPEAT_SPECIAL | ML_SPAC_MASK | ML_FIRSTSIDEONLY));
 
 		}
diff --git a/src/fragglescript/t_load.cpp b/src/fragglescript/t_load.cpp
index 0f3d8417b..b3b38543d 100644
--- a/src/fragglescript/t_load.cpp
+++ b/src/fragglescript/t_load.cpp
@@ -43,6 +43,7 @@
 #include "cmdlib.h"
 #include "p_lnspec.h"
 #include "gi.h"
+#include "g_levellocals.h"
 #include "xlat/xlat.h"
 
 void T_Init();
diff --git a/src/fragglescript/t_script.cpp b/src/fragglescript/t_script.cpp
index 0469e5063..b5c21632b 100644
--- a/src/fragglescript/t_script.cpp
+++ b/src/fragglescript/t_script.cpp
@@ -55,6 +55,7 @@
 #include "doomerrors.h"
 #include "doomstat.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/g_game.cpp b/src/g_game.cpp
index d80360193..6565d5324 100644
--- a/src/g_game.cpp
+++ b/src/g_game.cpp
@@ -91,6 +91,7 @@
 #include <zlib.h>
 
 #include "g_hub.h"
+#include "g_levellocals.h"
 
 
 static FRandom pr_dmspawn ("DMSpawn");
@@ -2241,7 +2242,7 @@ void G_DoSaveGame (bool okForQuicksave, FString filename, const char *descriptio
 
 	// Do not even try, if we're not in a level. (Can happen after
 	// a demo finishes playback.)
-	if (lines == NULL || level.sectors.Size() == 0 || gamestate != GS_LEVEL)
+	if (level.lines.Size() == 0 || level.sectors.Size() == 0 || gamestate != GS_LEVEL)
 	{
 		return;
 	}
diff --git a/src/g_hub.cpp b/src/g_hub.cpp
index cabcef2d3..e87dcff7d 100644
--- a/src/g_hub.cpp
+++ b/src/g_hub.cpp
@@ -44,6 +44,7 @@
 #include "gstrings.h"
 #include "wi_stuff.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 
 //==========================================================================
diff --git a/src/g_inventory/a_artifacts.cpp b/src/g_inventory/a_artifacts.cpp
index c859666d4..80ddac56d 100644
--- a/src/g_inventory/a_artifacts.cpp
+++ b/src/g_inventory/a_artifacts.cpp
@@ -22,6 +22,7 @@
 #include "serializer.h"
 #include "r_utility.h"
 #include "virtual.h"
+#include "g_levellocals.h"
 
 #include "r_data/colormaps.h"
 
diff --git a/src/g_inventory/a_pickups.cpp b/src/g_inventory/a_pickups.cpp
index c963fd918..e7a21fee6 100644
--- a/src/g_inventory/a_pickups.cpp
+++ b/src/g_inventory/a_pickups.cpp
@@ -22,6 +22,7 @@
 #include "virtual.h"
 #include "a_ammo.h"
 #include "c_functions.h"
+#include "g_levellocals.h"
 
 EXTERN_CVAR(Bool, sv_unlimited_pickup)
 
diff --git a/src/g_level.cpp b/src/g_level.cpp
index b0636d4d6..7e60a7ac9 100644
--- a/src/g_level.cpp
+++ b/src/g_level.cpp
@@ -88,6 +88,7 @@
 #include "gi.h"
 
 #include "g_hub.h"
+#include "g_levellocals.h"
 
 #include <string.h>
 
diff --git a/src/g_level.h b/src/g_level.h
index 5808df138..6274c22b0 100644
--- a/src/g_level.h
+++ b/src/g_level.h
@@ -376,77 +376,6 @@ struct level_info_t
 	}
 };
 
-struct FLevelLocals
-{
-	void Tick ();
-	void AddScroller (int secnum);
-
-	BYTE		md5[16];			// for savegame validation. If the MD5 does not match the savegame won't be loaded.
-	int			time;			// time in the hub
-	int			maptime;		// time in the map
-	int			totaltime;		// time in the game
-	int			starttime;
-	int			partime;
-	int			sucktime;
-
-	level_info_t *info;
-	int			cluster;
-	int			clusterflags;
-	int			levelnum;
-	int			lumpnum;
-	FString		LevelName;
-	FString		MapName;			// the lump name (E1M1, MAP01, etc)
-	FString		NextMap;			// go here when using the regular exit
-	FString		NextSecretMap;		// map to go to when used secret exit
-	EMapType	maptype;
-
-	TStaticArray<sector_t> sectors;
-
-	DWORD		flags;
-	DWORD		flags2;
-	DWORD		flags3;
-
-	DWORD		fadeto;					// The color the palette fades to (usually black)
-	DWORD		outsidefog;				// The fog for sectors with sky ceilings
-
-	FString		Music;
-	int			musicorder;
-	int			cdtrack;
-	unsigned int cdid;
-	FTextureID	skytexture1;
-	FTextureID	skytexture2;
-
-	float		skyspeed1;				// Scrolling speed of sky textures, in pixels per ms
-	float		skyspeed2;
-
-	int			total_secrets;
-	int			found_secrets;
-
-	int			total_items;
-	int			found_items;
-
-	int			total_monsters;
-	int			killed_monsters;
-
-	double		gravity;
-	double		aircontrol;
-	double		airfriction;
-	int			airsupply;
-	int			DefaultEnvironment;		// Default sound environment.
-
-	TArray<DVector2>	Scrolls;		// NULL if no DScrollers in this level
-
-	SBYTE		WallVertLight;			// Light diffs for vert/horiz walls
-	SBYTE		WallHorizLight;
-
-	bool		FromSnapshot;			// The current map was restored from a snapshot
-
-	double		teamdamage;
-
-	bool		IsJumpingAllowed() const;
-	bool		IsCrouchingAllowed() const;
-	bool		IsFreelookAllowed() const;
-};
 
 struct cluster_info_t
 {
@@ -476,8 +405,6 @@ struct cluster_info_t
 #define CLUSTER_LOOKUPCLUSTERNAME 0x00000080	// Cluster name is the name of a language string
 #define CLUSTER_ALLOWINTERMISSION 0x00000100  // Allow intermissions between levels in a hub.
 
-extern FLevelLocals level;
-
 extern TArray<level_info_t> wadlevelinfos;
 extern TArray<cluster_info_t> wadclusterinfos;
 
diff --git a/src/g_levellocals.h b/src/g_levellocals.h
new file mode 100644
index 000000000..08b18145d
--- /dev/null
+++ b/src/g_levellocals.h
@@ -0,0 +1,101 @@
+#pragma once
+
+#include "g_level.h"
+#include "r_defs.h"
+
+struct FLevelLocals
+{
+	void Tick ();
+	void AddScroller (int secnum);
+
+	BYTE		md5[16];			// for savegame validation. If the MD5 does not match the savegame won't be loaded.
+	int			time;			// time in the hub
+	int			maptime;		// time in the map
+	int			totaltime;		// time in the game
+	int			starttime;
+	int			partime;
+	int			sucktime;
+
+	level_info_t *info;
+	int			cluster;
+	int			clusterflags;
+	int			levelnum;
+	int			lumpnum;
+	FString		LevelName;
+	FString		MapName;			// the lump name (E1M1, MAP01, etc)
+	FString		NextMap;			// go here when using the regular exit
+	FString		NextSecretMap;		// map to go to when used secret exit
+	EMapType	maptype;
+
+	TStaticArray<vertex_t> vertexes;
+	TStaticArray<sector_t> sectors;
+	TStaticArray<line_t> lines;
+	TStaticArray<side_t> sides;
+
+	DWORD		flags;
+	DWORD		flags2;
+	DWORD		flags3;
+
+	DWORD		fadeto;					// The color the palette fades to (usually black)
+	DWORD		outsidefog;				// The fog for sectors with sky ceilings
+
+	FString		Music;
+	int			musicorder;
+	int			cdtrack;
+	unsigned int cdid;
+	FTextureID	skytexture1;
+	FTextureID	skytexture2;
+
+	float		skyspeed1;				// Scrolling speed of sky textures, in pixels per ms
+	float		skyspeed2;
+
+	int			total_secrets;
+	int			found_secrets;
+
+	int			total_items;
+	int			found_items;
+
+	int			total_monsters;
+	int			killed_monsters;
+
+	double		gravity;
+	double		aircontrol;
+	double		airfriction;
+	int			airsupply;
+	int			DefaultEnvironment;		// Default sound environment.
+
+	TArray<DVector2>	Scrolls;		// NULL if no DScrollers in this level
+
+	SBYTE		WallVertLight;			// Light diffs for vert/horiz walls
+	SBYTE		WallHorizLight;
+
+	bool		FromSnapshot;			// The current map was restored from a snapshot
+
+	double		teamdamage;
+
+	bool		IsJumpingAllowed() const;
+	bool		IsCrouchingAllowed() const;
+	bool		IsFreelookAllowed() const;
+};
+
+extern FLevelLocals level;
+
+inline int vertex_t::Index() const
+{
+	return int(this - &level.vertexes[0]);
+}
+
+inline int side_t::Index() const
+{
+	return int(this - &level.sides[0]);
+}
+
+inline int line_t::Index() const
+{
+	return int(this - &level.lines[0]);
+}
+
+inline int sector_t::Index() const 
+{ 
+	return int(this - &level.sectors[0]); 
+}
diff --git a/src/g_mapinfo.cpp b/src/g_mapinfo.cpp
index 6a6076565..3fab0bd0d 100644
--- a/src/g_mapinfo.cpp
+++ b/src/g_mapinfo.cpp
@@ -51,6 +51,7 @@
 #include "autosegs.h"
 #include "version.h"
 #include "v_text.h"
+#include "g_levellocals.h"
 
 TArray<cluster_info_t> wadclusterinfos;
 TArray<level_info_t> wadlevelinfos;
diff --git a/src/g_shared/a_decals.cpp b/src/g_shared/a_decals.cpp
index bfbe6d13d..5ac3cb452 100644
--- a/src/g_shared/a_decals.cpp
+++ b/src/g_shared/a_decals.cpp
@@ -47,6 +47,7 @@
 #include "serializer.h"
 #include "doomdata.h"
 #include "r_state.h"
+#include "g_levellocals.h"
 
 static double DecalWidth, DecalLeft, DecalRight;
 static double SpreadZ;
@@ -415,7 +416,7 @@ void DBaseDecal::SpreadLeft (double r, vertex_t *v1, side_t *feelwall, F3DFloor
 		double x = v1->fX();
 		double y = v1->fY();
 
-		feelwall = &sides[feelwall->LeftSide];
+		feelwall = &level.sides[feelwall->LeftSide];
 		GetWallStuff (feelwall, v1, ldx, ldy);
 		double wallsize = Length (ldx, ldy);
 		r += DecalLeft;
@@ -455,7 +456,7 @@ void DBaseDecal::SpreadRight (double r, side_t *feelwall, double wallsize, F3DFl
 
 	while (r > wallsize && feelwall->RightSide != NO_SIDE)
 	{
-		feelwall = &sides[feelwall->RightSide];
+		feelwall = &level.sides[feelwall->RightSide];
 
 		side_t *nextwall = NextWall (feelwall);
 		if (nextwall != NULL && nextwall->LeftSide != NO_SIDE)
diff --git a/src/g_shared/a_fastprojectile.cpp b/src/g_shared/a_fastprojectile.cpp
index fb0faef0f..3bfaf8d94 100644
--- a/src/g_shared/a_fastprojectile.cpp
+++ b/src/g_shared/a_fastprojectile.cpp
@@ -7,6 +7,7 @@
 #include "b_bot.h"
 #include "p_checkposition.h"
 #include "virtual.h"
+#include "g_levellocals.h"
 
 IMPLEMENT_CLASS(AFastProjectile, false, false)
 
diff --git a/src/g_shared/a_flashfader.cpp b/src/g_shared/a_flashfader.cpp
index 3e0b939e0..006b7ef84 100644
--- a/src/g_shared/a_flashfader.cpp
+++ b/src/g_shared/a_flashfader.cpp
@@ -2,6 +2,7 @@
 #include "g_level.h"
 #include "d_player.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 IMPLEMENT_CLASS(DFlashFader, false, true)
 
diff --git a/src/g_shared/a_lightning.cpp b/src/g_shared/a_lightning.cpp
index 1598b87f0..deeb8405b 100644
--- a/src/g_shared/a_lightning.cpp
+++ b/src/g_shared/a_lightning.cpp
@@ -10,6 +10,7 @@
 #include "g_level.h"
 #include "r_state.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 static FRandom pr_lightning ("Lightning");
 
diff --git a/src/g_shared/a_morph.cpp b/src/g_shared/a_morph.cpp
index 935efa2db..b48a126cd 100644
--- a/src/g_shared/a_morph.cpp
+++ b/src/g_shared/a_morph.cpp
@@ -16,6 +16,7 @@
 #include "d_player.h"
 #include "a_armor.h"
 #include "r_data/sprites.h"
+#include "g_levellocals.h"
 
 static FRandom pr_morphmonst ("MorphMonster");
 
diff --git a/src/g_shared/a_movingcamera.cpp b/src/g_shared/a_movingcamera.cpp
index c09d93fd5..f32550f2d 100644
--- a/src/g_shared/a_movingcamera.cpp
+++ b/src/g_shared/a_movingcamera.cpp
@@ -38,6 +38,7 @@
 #include "p_lnspec.h"
 #include "doomstat.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 /*
 == InterpolationPoint: node along a camera's path
diff --git a/src/g_shared/a_randomspawner.cpp b/src/g_shared/a_randomspawner.cpp
index d5a396d0d..9be5cac7b 100644
--- a/src/g_shared/a_randomspawner.cpp
+++ b/src/g_shared/a_randomspawner.cpp
@@ -16,6 +16,7 @@
 #include "v_text.h"
 #include "doomstat.h"
 #include "doomdata.h"
+#include "g_levellocals.h"
 
 #define MAX_RANDOMSPAWNERS_RECURSION 32 // Should be largely more than enough, honestly.
 static FRandom pr_randomspawn("RandomSpawn");
diff --git a/src/g_shared/sbarinfo.cpp b/src/g_shared/sbarinfo.cpp
index c06abf90d..fb7d42a46 100644
--- a/src/g_shared/sbarinfo.cpp
+++ b/src/g_shared/sbarinfo.cpp
@@ -60,6 +60,7 @@
 #include "version.h"
 #include "cmdlib.h"
 #include "a_ammo.h"
+#include "g_levellocals.h"
 
 #define ARTIFLASH_OFFSET (statusBar->invBarOffset+6)
 enum
diff --git a/src/g_shared/shared_hud.cpp b/src/g_shared/shared_hud.cpp
index a061dbf59..0c9b74255 100644
--- a/src/g_shared/shared_hud.cpp
+++ b/src/g_shared/shared_hud.cpp
@@ -55,6 +55,7 @@
 #include "d_player.h"
 #include "r_utility.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 #include <time.h>
 
diff --git a/src/g_shared/shared_sbar.cpp b/src/g_shared/shared_sbar.cpp
index c288a05c8..cb3ada8e9 100644
--- a/src/g_shared/shared_sbar.cpp
+++ b/src/g_shared/shared_sbar.cpp
@@ -55,6 +55,7 @@
 #include "gstrings.h"
 #include "r_utility.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 #include "../version.h"
 
diff --git a/src/g_skill.cpp b/src/g_skill.cpp
index 70daadc23..d158fa4cd 100644
--- a/src/g_skill.cpp
+++ b/src/g_skill.cpp
@@ -43,6 +43,7 @@
 #include "v_font.h"
 #include "m_fixed.h"
 #include "gstrings.h"
+#include "g_levellocals.h"
 
 TArray<FSkillInfo> AllSkills;
 int DefaultSkill = -1;
diff --git a/src/g_strife/strife_sbar.cpp b/src/g_strife/strife_sbar.cpp
index ccf17f8f1..110bcfbe9 100644
--- a/src/g_strife/strife_sbar.cpp
+++ b/src/g_strife/strife_sbar.cpp
@@ -19,6 +19,7 @@
 #include "colormatcher.h"
 #include "v_palette.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 // Number of tics to move the popscreen up and down.
 #define POP_TIME (TICRATE/8)
diff --git a/src/gl/compatibility/gl_20.cpp b/src/gl/compatibility/gl_20.cpp
index 0f9ee5f43..eeb5572c1 100644
--- a/src/gl/compatibility/gl_20.cpp
+++ b/src/gl/compatibility/gl_20.cpp
@@ -38,6 +38,7 @@
 #include "i_system.h"
 #include "v_text.h"
 #include "r_utility.h"
+#include "g_levellocals.h"
 #include "gl/dynlights/gl_dynlight.h"
 #include "gl/utility/gl_geometric.h"
 #include "gl/renderer/gl_renderer.h"
diff --git a/src/gl/data/gl_data.cpp b/src/gl/data/gl_data.cpp
index e8c5f22bb..07fac1b2e 100644
--- a/src/gl/data/gl_data.cpp
+++ b/src/gl/data/gl_data.cpp
@@ -41,6 +41,7 @@
 #include "g_level.h"
 #include "doomstat.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_interface.h"
 #include "gl/renderer/gl_renderer.h"
@@ -547,7 +548,7 @@ CCMD(dumpgeometry)
 				{
 				Printf(PRINT_LOG, "      (%4.4f, %4.4f), (%4.4f, %4.4f) - seg %d, linedef %d, side %d", 
 					seg->v1->fX(), seg->v1->fY(), seg->v2->fX(), seg->v2->fY(),
-					int(seg-segs), int(seg->linedef-lines), seg->sidedef != seg->linedef->sidedef[0]);
+					int(seg-segs), seg->linedef->Index(), seg->sidedef != seg->linedef->sidedef[0]);
 				}
 				else
 				{
diff --git a/src/gl/data/gl_portaldata.cpp b/src/gl/data/gl_portaldata.cpp
index 71b10b4bb..c705da589 100644
--- a/src/gl/data/gl_portaldata.cpp
+++ b/src/gl/data/gl_portaldata.cpp
@@ -38,6 +38,7 @@
 #include "gi.h"
 #include "g_level.h"
 #include "a_sharedglobal.h"
+#include "g_levellocals.h"
 
 #include "gl/renderer/gl_renderer.h"
 #include "gl/data/gl_data.h"
diff --git a/src/gl/data/gl_setup.cpp b/src/gl/data/gl_setup.cpp
index 3fc022cf8..6bdf57d4c 100644
--- a/src/gl/data/gl_setup.cpp
+++ b/src/gl/data/gl_setup.cpp
@@ -40,6 +40,7 @@
 #include "gi.h"
 #include "p_setup.h"
 #include "g_level.h"
+#include "g_levellocals.h"
 
 #include "gl/renderer/gl_renderer.h"
 #include "gl/data/gl_data.h"
@@ -402,51 +403,50 @@ static void InitVertexData()
 
 	int i,j,k;
 
-	vt_sectorlists = new TArray<int>[numvertexes];
+	vt_sectorlists = new TArray<int>[level.vertexes.Size()];
 
 
-	for(i=0;i<numlines;i++)
+	for(auto &line : level.lines)
 	{
-		line_t * line = &lines[i];
-
 		for(j=0;j<2;j++)
 		{
-			vertex_t * v = j==0? line->v1 : line->v2;
+			vertex_t * v = j==0? line.v1 : line.v2;
 
 			for(k=0;k<2;k++)
 			{
-				sector_t * sec = k==0? line->frontsector : line->backsector;
+				sector_t * sec = k==0? line.frontsector : line.backsector;
 
 				if (sec)
 				{
 					extsector_t::xfloor &x = sec->e->XFloor;
 
-					AddToVertex(sec, vt_sectorlists[v-vertexes]);
-					if (sec->heightsec) AddToVertex(sec->heightsec, vt_sectorlists[v-vertexes]);
+					AddToVertex(sec, vt_sectorlists[v->Index()]);
+					if (sec->heightsec) AddToVertex(sec->heightsec, vt_sectorlists[v->Index()]);
 				}
 			}
 		}
 	}
 
-	for(i=0;i<numvertexes;i++)
+	for(i=0;i<level.vertexes.Size();i++)
 	{
+		auto vert = level.vertexes[i];
 		int cnt = vt_sectorlists[i].Size();
 
-		vertexes[i].dirty = true;
-		vertexes[i].numheights=0;
+		vert.dirty = true;
+		vert.numheights=0;
 		if (cnt>1)
 		{
-			vertexes[i].numsectors= cnt;
-			vertexes[i].sectors=new sector_t*[cnt];
-			vertexes[i].heightlist = new float[cnt*2];
+			vert.numsectors= cnt;
+			vert.sectors=new sector_t*[cnt];
+			vert.heightlist = new float[cnt*2];
 			for(int j=0;j<cnt;j++)
 			{
-				vertexes[i].sectors[j] = &level.sectors[vt_sectorlists[i][j]];
+				vert.sectors[j] = &level.sectors[vt_sectorlists[i][j]];
 			}
 		}
 		else
 		{
-			vertexes[i].numsectors=0;
+			vert.numsectors=0;
 		}
 	}
 
@@ -461,8 +461,8 @@ static void InitVertexData()
 
 static void GetSideVertices(int sdnum, DVector2 *v1, DVector2 *v2)
 {
-	line_t *ln = sides[sdnum].linedef;
-	if (ln->sidedef[0] == &sides[sdnum]) 
+	line_t *ln = level.sides[sdnum].linedef;
+	if (ln->sidedef[0] == &level.sides[sdnum])
 	{
 		*v1 = ln->v1->fPos();
 		*v2 = ln->v2->fPos();
@@ -489,54 +489,25 @@ static int segcmp(const void *a, const void *b)
 
 static void PrepareSegs()
 {
+	auto numsides = level.sides.Size();
 	int *segcount = new int[numsides];
 	int realsegs = 0;
 
 	// Get floatng point coordinates of vertices
-	for(int i = 0; i < numvertexes; i++)
+	for(auto &v : level.vertexes)
 	{
-		vertexes[i].dirty = true;
+		v.dirty = true;
 	}
 
 	// count the segs
 	memset(segcount, 0, numsides * sizeof(int));
-	
-	// set up the extra data in case the map was loaded with regular nodes that might pass as GL nodes.
-	if (glsegextras == NULL)
-	{
-		for(int i=0;i<numsegs;i++)
-		{
-			segs[i].PartnerSeg = NULL;
-		}
-		for (int i=0; i<numsubsectors; i++)
-		{
-			int seg = int(subsectors[i].firstline-segs);
-			for(DWORD j=0;j<subsectors[i].numlines;j++)
-			{
-				segs[j+seg].Subsector = &subsectors[i];
-			}
-		}
-	}
-	else
-	{
-		for(int i=0;i<numsegs;i++)
-		{
-			seg_t *seg = &segs[i];
-
-			// Account for ZDoom space optimizations that cannot be done for GL
-			unsigned int partner= glsegextras[i].PartnerSeg;
-			if (partner < unsigned(numsegs))  seg->PartnerSeg = &segs[partner];
-			else seg->PartnerSeg = NULL;
-			seg->Subsector = glsegextras[i].Subsector;
-		}
-	}
 
 	for(int i=0;i<numsegs;i++)
 	{
 		seg_t *seg = &segs[i];
 
 		if (seg->sidedef == NULL) continue;	// miniseg
-		int sidenum = int(seg->sidedef - sides);
+		int sidenum = seg->sidedef->Index();
 
 		realsegs++;
 		segcount[sidenum]++;
@@ -550,13 +521,13 @@ static void PrepareSegs()
 	}
 
 	// allocate memory
-	sides[0].segs = new seg_t*[realsegs];
-	sides[0].numsegs = 0;
+	level.sides[0].segs = new seg_t*[realsegs];
+	level.sides[0].numsegs = 0;
 
 	for(int i = 1; i < numsides; i++)
 	{
-		sides[i].segs = sides[i-1].segs + segcount[i-1];
-		sides[i].numsegs = 0;
+		level.sides[i].segs = level.sides[i-1].segs + segcount[i-1];
+		level.sides[i].numsegs = 0;
 	}
 	delete [] segcount;
 
@@ -570,7 +541,7 @@ static void PrepareSegs()
 	// sort the segs
 	for(int i = 0; i < numsides; i++)
 	{
-		if (sides[i].numsegs > 1) qsort(sides[i].segs, sides[i].numsegs, sizeof(seg_t*), segcmp);
+		if (level.sides[i].numsegs > 1) qsort(level.sides[i].segs, level.sides[i].numsegs, sizeof(seg_t*), segcmp);
 	}
 }
 
@@ -586,8 +557,8 @@ void gl_PreprocessLevel()
 	PrepareSegs();
 	PrepareSectorData();
 	InitVertexData();
-	int *checkmap = new int[numvertexes];
-	memset(checkmap, -1, sizeof(int)*numvertexes);
+	int *checkmap = new int[level.vertexes.Size()];
+	memset(checkmap, -1, sizeof(int)*level.vertexes.Size());
 	for(auto &sec : level.sectors) 
 	{
 		int i = sec.sectornum;
@@ -598,21 +569,21 @@ void gl_PreprocessLevel()
 		{
 			if (l->sidedef[0]->Flags & WALLF_POLYOBJ) continue;	// don't bother with polyobjects
 
-			int vtnum1 = int(l->v1 - vertexes);
-			int vtnum2 = int(l->v2 - vertexes);
+			int vtnum1 = l->v1->Index();
+			int vtnum2 = l->v2->Index();
 
 			if (checkmap[vtnum1] < i)
 			{
 				checkmap[vtnum1] = i;
-				sec.e->vertices.Push(&vertexes[vtnum1]);
-				vertexes[vtnum1].dirty = true;
+				sec.e->vertices.Push(&level.vertexes[vtnum1]);
+				level.vertexes[vtnum1].dirty = true;
 			}
 
 			if (checkmap[vtnum2] < i)
 			{
 				checkmap[vtnum2] = i;
-				sec.e->vertices.Push(&vertexes[vtnum2]);
-				vertexes[vtnum2].dirty = true;
+				sec.e->vertices.Push(&level.vertexes[vtnum2]);
+				level.vertexes[vtnum2].dirty = true;
 			}
 		}
 	}
@@ -652,27 +623,24 @@ void gl_CleanLevelData()
 		mo=next;
 	}
 
-	if (vertexes != NULL)
+	for(auto &v : level.vertexes) if (v.numsectors > 0)
 	{
-		for(int i = 0; i < numvertexes; i++) if (vertexes[i].numsectors > 0)
+		if (v.sectors != nullptr)
 		{
-			if (vertexes[i].sectors != NULL)
-			{
-				delete [] vertexes[i].sectors;
-				vertexes[i].sectors = NULL;
-			}
-			if (vertexes[i].heightlist != NULL)
-			{
-				delete [] vertexes[i].heightlist;
-				vertexes[i].heightlist = NULL;
-			}
+			delete [] v.sectors;
+			v.sectors = nullptr;
+		}
+		if (v.heightlist != nullptr)
+		{
+			delete [] v.heightlist;
+			v.heightlist = nullptr;
 		}
 	}
 
-	if (sides && sides[0].segs)
+	if (level.sides.Size() > 0 && level.sides[0].segs)
 	{
-		delete [] sides[0].segs;
-		sides[0].segs = NULL;
+		delete [] level.sides[0].segs;
+		level.sides[0].segs = NULL;
 	}
 	if (level.sectors.Size() > 0 && level.sectors[0].subsectors) 
 	{
@@ -712,7 +680,7 @@ CCMD(listmapsections)
 		{
 			if (subsectors[j].mapsection == i)
 			{
-				Printf("Mapsection %d, sector %d, line %d\n", i, subsectors[j].render_sector->sectornum, int(subsectors[j].firstline->linedef-lines));
+				Printf("Mapsection %d, sector %d, line %d\n", i, subsectors[j].render_sector->Index(), subsectors[j].firstline->linedef->Index());
 				break;
 			}
 		}
diff --git a/src/gl/data/gl_vertexbuffer.cpp b/src/gl/data/gl_vertexbuffer.cpp
index a645fbff4..4973ad39d 100644
--- a/src/gl/data/gl_vertexbuffer.cpp
+++ b/src/gl/data/gl_vertexbuffer.cpp
@@ -31,6 +31,7 @@
 #include "r_state.h"
 #include "m_argv.h"
 #include "c_cvars.h"
+#include "g_levellocals.h"
 #include "gl/system/gl_interface.h"
 #include "gl/renderer/gl_renderer.h"
 #include "gl/shaders/gl_shader.h"
diff --git a/src/gl/dynlights/a_dynlight.cpp b/src/gl/dynlights/a_dynlight.cpp
index 82c8c4e54..1283cc972 100644
--- a/src/gl/dynlights/a_dynlight.cpp
+++ b/src/gl/dynlights/a_dynlight.cpp
@@ -71,6 +71,7 @@
 #include "portal.h"
 #include "doomstat.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 
 #include "gl/renderer/gl_renderer.h"
diff --git a/src/gl/dynlights/gl_dynlight.cpp b/src/gl/dynlights/gl_dynlight.cpp
index bc107c60e..a0d9292a9 100644
--- a/src/gl/dynlights/gl_dynlight.cpp
+++ b/src/gl/dynlights/gl_dynlight.cpp
@@ -49,6 +49,7 @@
 #include "zstring.h"
 #include "d_dehacked.h"
 #include "v_text.h"
+#include "g_levellocals.h"
 
 
 #include "gl/dynlights/gl_dynlight.h"
diff --git a/src/gl/models/gl_models.cpp b/src/gl/models/gl_models.cpp
index f3dfbd569..ce6b22ee8 100644
--- a/src/gl/models/gl_models.cpp
+++ b/src/gl/models/gl_models.cpp
@@ -37,6 +37,7 @@
 #include "g_level.h"
 #include "r_state.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 //#include "resources/voxels.h"
 //#include "gl/gl_intern.h"
 
diff --git a/src/gl/renderer/gl_lightdata.cpp b/src/gl/renderer/gl_lightdata.cpp
index d09484a1f..3ba557737 100644
--- a/src/gl/renderer/gl_lightdata.cpp
+++ b/src/gl/renderer/gl_lightdata.cpp
@@ -38,6 +38,7 @@
 #include "p_local.h"
 #include "g_level.h"
 #include "r_sky.h"
+#include "g_levellocals.h"
 
 // externally settable lighting properties
 static float distfogtable[2][256];	// light to fog conversion table for black fog
diff --git a/src/gl/scene/gl_bsp.cpp b/src/gl/scene/gl_bsp.cpp
index da6077049..af4d46d61 100644
--- a/src/gl/scene/gl_bsp.cpp
+++ b/src/gl/scene/gl_bsp.cpp
@@ -87,7 +87,7 @@ static sector_t *currentsector;
 static void AddLine (seg_t *seg, bool portalclip)
 {
 #ifdef _DEBUG
-	if (seg->linedef - lines == 38)
+	if (seg->linedef->Index() == 38)
 	{
 		int a = 0;
 	}
diff --git a/src/gl/scene/gl_drawinfo.cpp b/src/gl/scene/gl_drawinfo.cpp
index 5fc775603..7e9a3e6d2 100644
--- a/src/gl/scene/gl_drawinfo.cpp
+++ b/src/gl/scene/gl_drawinfo.cpp
@@ -32,6 +32,7 @@
 #include "r_utility.h"
 #include "r_state.h"
 #include "doomstat.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_cvars.h"
 #include "gl/data/gl_data.h"
diff --git a/src/gl/scene/gl_flats.cpp b/src/gl/scene/gl_flats.cpp
index efadbcebe..c4296c50d 100644
--- a/src/gl/scene/gl_flats.cpp
+++ b/src/gl/scene/gl_flats.cpp
@@ -35,6 +35,7 @@
 #include "d_player.h"
 #include "portal.h"
 #include "templates.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_interface.h"
 #include "gl/system/gl_cvars.h"
diff --git a/src/gl/scene/gl_renderhacks.cpp b/src/gl/scene/gl_renderhacks.cpp
index 9242df2a9..4dd7b7d81 100644
--- a/src/gl/scene/gl_renderhacks.cpp
+++ b/src/gl/scene/gl_renderhacks.cpp
@@ -30,7 +30,7 @@
 #include "r_defs.h"
 #include "r_sky.h"
 #include "g_level.h"
-
+#include "g_levellocals.h"
 
 #include "gl/renderer/gl_renderer.h"
 #include "gl/data/gl_data.h"
diff --git a/src/gl/scene/gl_scene.cpp b/src/gl/scene/gl_scene.cpp
index 13cd2eac4..7f1432e14 100644
--- a/src/gl/scene/gl_scene.cpp
+++ b/src/gl/scene/gl_scene.cpp
@@ -43,6 +43,7 @@
 #include "p_local.h"
 #include "gl/gl_functions.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 #include "gl/dynlights/gl_lightbuffer.h"
 #include "gl/system/gl_interface.h"
diff --git a/src/gl/scene/gl_sky.cpp b/src/gl/scene/gl_sky.cpp
index 2a2952548..19d1c9127 100644
--- a/src/gl/scene/gl_sky.cpp
+++ b/src/gl/scene/gl_sky.cpp
@@ -28,6 +28,7 @@
 #include "r_utility.h"
 #include "doomdata.h"
 #include "portal.h"
+#include "g_levellocals.h"
 #include "gl/gl_functions.h"
 
 #include "gl/data/gl_data.h"
@@ -51,7 +52,7 @@ void GLSkyInfo::init(int sky1, PalEntry FadeColor)
 	memset(this, 0, sizeof(*this));
 	if ((sky1 & PL_SKYFLAT) && (sky1 & (PL_SKYFLAT - 1)))
 	{
-		const line_t *l = &lines[(sky1&(PL_SKYFLAT - 1)) - 1];
+		const line_t *l = &level.lines[(sky1&(PL_SKYFLAT - 1)) - 1];
 		const side_t *s = l->sidedef[0];
 		int pos;
 
diff --git a/src/gl/scene/gl_sprite.cpp b/src/gl/scene/gl_sprite.cpp
index b0cfcebe3..198dfea6e 100644
--- a/src/gl/scene/gl_sprite.cpp
+++ b/src/gl/scene/gl_sprite.cpp
@@ -36,6 +36,7 @@
 #include "r_utility.h"
 #include "a_pickups.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_interface.h"
 #include "gl/system/gl_framebuffer.h"
diff --git a/src/gl/scene/gl_walls.cpp b/src/gl/scene/gl_walls.cpp
index 9d471b72d..5965eebc3 100644
--- a/src/gl/scene/gl_walls.cpp
+++ b/src/gl/scene/gl_walls.cpp
@@ -33,6 +33,7 @@
 #include "p_maputl.h"
 #include "doomdata.h"
 #include "portal.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_cvars.h"
 #include "gl/renderer/gl_lightdata.h"
@@ -326,7 +327,7 @@ void GLWall::SplitWall(sector_t * frontsector, bool translucent)
 	//::SplitWall.Clock();
 
 #ifdef _DEBUG
-	if (seg->linedef-lines==1)
+	if (seg->linedef->Index() == 1)
 	{
 		int a = 0;
 	}
@@ -1414,7 +1415,7 @@ void GLWall::Process(seg_t *seg, sector_t * frontsector, sector_t * backsector)
 	sector_t * segback;
 
 #ifdef _DEBUG
-	if (seg->linedef - lines < 4)
+	if (seg->linedef->Index() == 1)
 	{
 		int a = 0;
 	}
@@ -1547,7 +1548,7 @@ void GLWall::Process(seg_t *seg, sector_t * frontsector, sector_t * backsector)
 			zbottom[1] = zfloor[1];
 			PutPortal(PORTALTYPE_LINETOLINE);
 		}
-		else if (seg->linedef->portaltransferred > 0)
+		else if (seg->linedef->GetTransferredPortal())
 		{
 			SkyLine(frontsector, seg->linedef);
 		}
diff --git a/src/gl/scene/gl_weapon.cpp b/src/gl/scene/gl_weapon.cpp
index 7662c7876..953509495 100644
--- a/src/gl/scene/gl_weapon.cpp
+++ b/src/gl/scene/gl_weapon.cpp
@@ -32,6 +32,7 @@
 #include "doomstat.h"
 #include "d_player.h"
 #include "g_level.h"
+#include "g_levellocals.h"
 
 #include "gl/system/gl_interface.h"
 #include "gl/system/gl_cvars.h"
diff --git a/src/gl/utility/gl_clock.cpp b/src/gl/utility/gl_clock.cpp
index 0dc9fd76c..68a2b06e5 100644
--- a/src/gl/utility/gl_clock.cpp
+++ b/src/gl/utility/gl_clock.cpp
@@ -48,6 +48,7 @@
 #include "c_dispatch.h"
 #include "r_utility.h"
 #include "v_video.h"
+#include "g_levellocals.h"
 #include "gl/utility/gl_clock.h"
 #include "gl/utility/gl_convert.h"
 
diff --git a/src/hu_scores.cpp b/src/hu_scores.cpp
index 35e18006d..1164eaf1c 100644
--- a/src/hu_scores.cpp
+++ b/src/hu_scores.cpp
@@ -50,6 +50,7 @@
 #include "gstrings.h"
 #include "d_net.h"
 #include "c_dispatch.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/intermission/intermission.cpp b/src/intermission/intermission.cpp
index 2aacd215b..2416f01c4 100644
--- a/src/intermission/intermission.cpp
+++ b/src/intermission/intermission.cpp
@@ -51,6 +51,7 @@
 #include "p_conversation.h"
 #include "menu/menu.h"
 #include "d_net.h"
+#include "g_levellocals.h"
 
 FIntermissionDescriptorList IntermissionDescriptors;
 
diff --git a/src/m_cheat.cpp b/src/m_cheat.cpp
index 53ae789c6..414fafba9 100644
--- a/src/m_cheat.cpp
+++ b/src/m_cheat.cpp
@@ -49,6 +49,7 @@
 #include "a_morph.h"
 #include "a_armor.h"
 #include "a_ammo.h"
+#include "g_levellocals.h"
 
 // [RH] Actually handle the cheat. The cheat code in st_stuff.c now just
 // writes some bytes to the network data stream, and the network code
diff --git a/src/menu/readthis.cpp b/src/menu/readthis.cpp
index b8a3837ee..f1e82cd51 100644
--- a/src/menu/readthis.cpp
+++ b/src/menu/readthis.cpp
@@ -37,6 +37,7 @@
 #include "v_video.h"
 #include "g_level.h"
 #include "gi.h"
+#include "g_levellocals.h"
 #include "textures/textures.h"
 
 class DReadThisMenu : public DMenu
diff --git a/src/nodebuild.h b/src/nodebuild.h
index 7e2a61aaa..9599bc0d2 100644
--- a/src/nodebuild.h
+++ b/src/nodebuild.h
@@ -209,10 +209,10 @@ public:
 		bool makeGLNodes);
 	~FNodeBuilder ();
 
-	void Extract (node_t *&nodes, int &nodeCount,
-		seg_t *&segs, glsegextra_t *&glsegextras, int &segCount,
+	void Extract(node_t *&nodes, int &nodeCount,
+		seg_t *&segs, int &segCount,
 		subsector_t *&ssecs, int &subCount,
-		vertex_t *&verts, int &vertCount);
+		TStaticArray<vertex_t> &vertexes);
 	const int *GetOldVertexTable();
 
 	// These are used for building sub-BSP trees for polyobjects.
diff --git a/src/nodebuild_extract.cpp b/src/nodebuild_extract.cpp
index c3f63c820..11332f049 100644
--- a/src/nodebuild_extract.cpp
+++ b/src/nodebuild_extract.cpp
@@ -53,14 +53,14 @@
 #endif
 
 void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
-	seg_t *&outSegs, glsegextra_t *&outSegExtras, int &segCount,
+	seg_t *&outSegs, int &segCount,
 	subsector_t *&outSubs, int &subCount,
-	vertex_t *&outVerts, int &vertCount)
+	TStaticArray<vertex_t> &outVerts)
 {
 	int i;
 
-	vertCount = Vertices.Size ();
-	outVerts = new vertex_t[vertCount];
+	int vertCount = Vertices.Size ();
+	outVerts.Alloc(vertCount);
 
 	for (i = 0; i < vertCount; ++i)
 	{
@@ -109,14 +109,13 @@ void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
 
 		for (i = 0; i < subCount; ++i)
 		{
-			DWORD numsegs = CloseSubsector (segs, i, outVerts);
+			DWORD numsegs = CloseSubsector (segs, i, &outVerts[0]);
 			outSubs[i].numlines = numsegs;
 			outSubs[i].firstline = (seg_t *)(size_t)(segs.Size() - numsegs);
 		}
 
 		segCount = segs.Size ();
 		outSegs = new seg_t[segCount];
-		outSegExtras = new glsegextra_t[segCount];
 
 		for (i = 0; i < segCount; ++i)
 		{
@@ -124,11 +123,11 @@ void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
 
 			if (segs[i].Partner != DWORD_MAX)
 			{
-				outSegExtras[i].PartnerSeg = Segs[segs[i].Partner].storedseg;
+				outSegs[i].PartnerSeg = &outSegs[Segs[segs[i].Partner].storedseg];
 			}
 			else
 			{
-				outSegExtras[i].PartnerSeg = DWORD_MAX;
+				outSegs[i].PartnerSeg = nullptr;
 			}
 		}
 	}
@@ -137,7 +136,6 @@ void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
 		memcpy (outSubs, &Subsectors[0], subCount*sizeof(subsector_t));
 		segCount = Segs.Size ();
 		outSegs = new seg_t[segCount];
-		outSegExtras = NULL;
 		for (i = 0; i < segCount; ++i)
 		{
 			const FPrivSeg *org = &Segs[SegList[i].SegNum];
@@ -145,12 +143,13 @@ void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
 
 			D(Printf(PRINT_LOG, "Seg %d: v1(%d) -> v2(%d)\n", i, org->v1, org->v2));
 
-			out->v1 = outVerts + org->v1;
-			out->v2 = outVerts + org->v2;
+			out->v1 = &outVerts[org->v1];
+			out->v2 = &outVerts[org->v2];
 			out->backsector = org->backsector;
 			out->frontsector = org->frontsector;
 			out->linedef = Level.Lines + org->linedef;
 			out->sidedef = Level.Sides + org->sidedef;
+			out->PartnerSeg = nullptr;
 		}
 	}
 	for (i = 0; i < subCount; ++i)
@@ -162,8 +161,8 @@ void FNodeBuilder::Extract (node_t *&outNodes, int &nodeCount,
 
 	for (i = 0; i < Level.NumLines; ++i)
 	{
-		Level.Lines[i].v1 = outVerts + (size_t)Level.Lines[i].v1;
-		Level.Lines[i].v2 = outVerts + (size_t)Level.Lines[i].v2;
+		Level.Lines[i].v1 = &outVerts[(size_t)Level.Lines[i].v1];
+		Level.Lines[i].v2 = &outVerts[(size_t)Level.Lines[i].v2];
 	}
 }
 
diff --git a/src/nodebuild_utility.cpp b/src/nodebuild_utility.cpp
index 02e280261..b6115f4c8 100644
--- a/src/nodebuild_utility.cpp
+++ b/src/nodebuild_utility.cpp
@@ -50,6 +50,7 @@
 #include "i_system.h"
 #include "po_man.h"
 #include "r_state.h"
+#include "g_levellocals.h"
 #include "math/cmath.h"
 
 static const int PO_LINE_START = 1;
@@ -186,7 +187,7 @@ int FNodeBuilder::CreateSeg (int linenum, int sidenum)
 	}
 	seg.linedef = linenum;
 	side_t *sd = Level.Lines[linenum].sidedef[sidenum];
-	seg.sidedef = sd != NULL? int(sd - sides) : int(NO_SIDE);
+	seg.sidedef = sd != NULL? sd->Index() : int(NO_SIDE);
 	seg.nextforvert = Vertices[seg.v1].segs;
 	seg.nextforvert2 = Vertices[seg.v2].segs2;
 
diff --git a/src/p_3dfloors.cpp b/src/p_3dfloors.cpp
index e4778e91d..c25d4a532 100644
--- a/src/p_3dfloors.cpp
+++ b/src/p_3dfloors.cpp
@@ -47,6 +47,7 @@
 #include "r_utility.h"
 #include "p_spec.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 EXTERN_CVAR(Int, vid_renderer)
 
@@ -850,16 +851,14 @@ void P_LineOpening_XFloors (FLineOpening &open, AActor * thing, const line_t *li
 void P_Spawn3DFloors (void)
 {
 	static int flagvals[] = {512, 2+512, 512+1024};
-	int i;
-	line_t * line;
 
-	for (i=0,line=lines;i<numlines;i++,line++)
+	for (auto &line : level.lines)
 	{
-		switch(line->special)
+		switch(line.special)
 		{
 		case ExtraFloor_LightOnly:
-			if (line->args[1] < 0 || line->args[1] > 2) line->args[1] = 0;
-			P_Set3DFloor(line, 3, flagvals[line->args[1]], 0);
+			if (line.args[1] < 0 || line.args[1] > 2) line.args[1] = 0;
+			P_Set3DFloor(&line, 3, flagvals[line.args[1]], 0);
 			break;
 
 		case Sector_Set3DFloor:
@@ -868,24 +867,24 @@ void P_Spawn3DFloors (void)
 			// In Doom format the translators can take full integers for the tag and the line ID always is the same as the tag.
 			if (level.maptype == MAPTYPE_HEXEN)	
 			{
-				if (line->args[1]&8)
+				if (line.args[1]&8)
 				{
-					tagManager.AddLineID(i, line->args[4]);
+					tagManager.AddLineID(line.Index(), line.args[4]);
 				}
 				else
 				{
-					line->args[0]+=256*line->args[4];
-					line->args[4]=0;
+					line.args[0]+=256*line.args[4];
+					line.args[4]=0;
 				}
 			}
-			P_Set3DFloor(line, line->args[1]&~8, line->args[2], line->args[3]);
+			P_Set3DFloor(&line, line.args[1]&~8, line.args[2], line.args[3]);
 			break;
 
 		default:
 			continue;
 		}
-		line->special=0;
-		line->args[0] = line->args[1] = line->args[2] = line->args[3] = line->args[4] = 0;
+		line.special=0;
+		line.args[0] = line.args[1] = line.args[2] = line.args[3] = line.args[4] = 0;
 	}
 	// kg3D - do it in software
 	for (auto &sec : level.sectors)
diff --git a/src/p_3dmidtex.cpp b/src/p_3dmidtex.cpp
index b775055d8..cb7f27a08 100644
--- a/src/p_3dmidtex.cpp
+++ b/src/p_3dmidtex.cpp
@@ -41,6 +41,7 @@
 #include "p_terrain.h"
 #include "p_maputl.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 
 //============================================================================
@@ -121,10 +122,10 @@ void P_Attach3dMidtexLinesToSector(sector_t *sector, int lineid, int tag, bool c
 	extsector_t::midtex::plane &scrollplane = ceiling? sector->e->Midtex.Ceiling : sector->e->Midtex.Floor;
 
 	// Bit arrays that mark whether a line or sector is to be attached.
-	BYTE *found_lines = new BYTE[(numlines+7)/8];
+	BYTE *found_lines = new BYTE[(level.lines.Size()+7)/8];
 	BYTE *found_sectors = new BYTE[(level.sectors.Size()+7)/8];
 
-	memset(found_lines, 0, sizeof (BYTE) * ((numlines+7)/8));
+	memset(found_lines, 0, sizeof (BYTE) * ((level.lines.Size()+7)/8));
 	memset(found_sectors, 0, sizeof (BYTE) * ((level.sectors.Size()+7)/8));
 
 	// mark all lines and sectors that are already attached to this one
@@ -132,13 +133,13 @@ void P_Attach3dMidtexLinesToSector(sector_t *sector, int lineid, int tag, bool c
 	// from the marker arrays.
 	for (unsigned i=0; i < scrollplane.AttachedLines.Size(); i++)
 	{
-		int line = int(scrollplane.AttachedLines[i] - lines);
+		int line = scrollplane.AttachedLines[i]->Index();
 		found_lines[line>>3] |= 1 << (line&7);
 	}
 
 	for (unsigned i=0; i < scrollplane.AttachedSectors.Size(); i++)
 	{
-		int sec = scrollplane.AttachedSectors[i]->sectornum;
+		int sec = scrollplane.AttachedSectors[i]->Index();
 		found_sectors[sec>>3] |= 1 << (sec&7);
 	}
 
@@ -151,7 +152,7 @@ void P_Attach3dMidtexLinesToSector(sector_t *sector, int lineid, int tag, bool c
 		int line;
 		while ((line = itr.Next()) >= 0)
 		{
-			line_t *ln = &lines[line];
+			line_t *ln = &level.lines[line];
 
 			if (ln->frontsector == NULL || ln->backsector == NULL || !(ln->flags & ML_3DMIDTEX))
 			{
@@ -176,24 +177,25 @@ void P_Attach3dMidtexLinesToSector(sector_t *sector, int lineid, int tag, bool c
 					// Only consider two-sided lines with the 3DMIDTEX flag
 					continue;
 				}
-				int lineno = int(ln-lines);
-				found_lines[lineno>>3] |= 1 << (lineno&7);
+				int lineno = ln->Index();
+				found_lines[lineno >> 3] |= 1 << (lineno & 7);
 			}
 		}
 	}
 
 
-	for(int i=0; i < numlines; i++)
+	for(unsigned i=0; i < level.lines.Size(); i++)
 	{
 		if (found_lines[i>>3] & (1 << (i&7)))
 		{
-			scrollplane.AttachedLines.Push(&lines[i]);
+			auto &line = level.lines[i];
+			scrollplane.AttachedLines.Push(&line);
 
-			v = lines[i].frontsector->sectornum;
+			v = line.frontsector->Index();
 			assert(v < (int)level.sectors.Size());
 			found_sectors[v>>3] |= 1 << (v&7);
 
-			v = lines[i].backsector->sectornum;
+			v = line.backsector->Index();
 			assert(v < (int)level.sectors.Size());
 			found_sectors[v>>3] |= 1 << (v&7);
 		}
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index d35714ca5..f1a0ae8bf 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -86,6 +86,7 @@
 #include "a_armor.h"
 #include "a_ammo.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 extern FILE *Logfile;
 
@@ -3284,7 +3285,7 @@ void DLevelScript::SetLineTexture (int lineid, int side, int position, int name)
 	int linenum = -1;
 	const char *texname = FBehavior::StaticLookupString (name);
 
-	if (texname == NULL)
+	if (texname == nullptr)
 		return;
 
 	side = !!side;
@@ -3296,8 +3297,8 @@ void DLevelScript::SetLineTexture (int lineid, int side, int position, int name)
 	{
 		side_t *sidedef;
 
-		sidedef = lines[linenum].sidedef[side];
-		if (sidedef == NULL)
+		sidedef = level.lines[linenum].sidedef[side];
+		if (sidedef == nullptr)
 			continue;
 
 		switch (position)
@@ -3332,16 +3333,14 @@ void DLevelScript::ReplaceTextures (int fromnamei, int tonamei, int flags)
 		picnum1 = TexMan.GetTexture (fromname, FTexture::TEX_Wall, FTextureManager::TEXMAN_Overridable);
 		picnum2 = TexMan.GetTexture (toname, FTexture::TEX_Wall, FTextureManager::TEXMAN_Overridable);
 
-		for (int i = 0; i < numsides; ++i)
+		for (auto &side : level.sides)
 		{
-			side_t *wal = &sides[i];
-
 			for(int j=0;j<3;j++)
 			{
 				static BYTE bits[]={NOT_TOP, NOT_MIDDLE, NOT_BOTTOM};
-				if (!(flags & bits[j]) && wal->GetTexture(j) == picnum1)
+				if (!(flags & bits[j]) && side.GetTexture(j) == picnum1)
 				{
-					wal->SetTexture(j, picnum2);
+					side.SetTexture(j, picnum2);
 				}
 			}
 		}
@@ -4428,14 +4427,14 @@ int DLevelScript::SideFromID(int id, int side)
 	{
 		if (activationline == NULL) return -1;
 		if (activationline->sidedef[side] == NULL) return -1;
-		return activationline->sidedef[side]->Index;
+		return activationline->sidedef[side]->UDMFIndex;
 	}
 	else
 	{
 		int line = P_FindFirstLineFromID(id);
 		if (line == -1) return -1;
-		if (lines[line].sidedef[side] == NULL) return -1;
-		return lines[line].sidedef[side]->Index;
+		if (level.lines[line].sidedef[side] == NULL) return -1;
+		return level.lines[line].sidedef[side]->UDMFIndex;
 	}
 }
 
@@ -4444,7 +4443,7 @@ int DLevelScript::LineFromID(int id)
 	if (id == 0)
 	{
 		if (activationline == NULL) return -1;
-		return int(activationline - lines);
+		return activationline->Index();
 	}
 	else
 	{
@@ -5695,7 +5694,7 @@ doplaysound:			if (funcIndex == ACSF_PlayActorSound)
 				FLineIdIterator itr(args[0]);
 				while ((line = itr.Next()) >= 0)
 				{
-					lines[line].activation = args[1];
+					level.lines[line].activation = args[1];
 				}
 			}
 			break;
@@ -5704,7 +5703,7 @@ doplaysound:			if (funcIndex == ACSF_PlayActorSound)
 			if (argCount > 0)
 			{
 				int line = P_FindFirstLineFromID(args[0]);
-				return line >= 0 ? lines[line].activation : 0;
+				return line >= 0 ? level.lines[line].activation : 0;
 			}
 			break;
 
@@ -7742,7 +7741,7 @@ scriptwait:
 			if (activationline != NULL)
 			{
 				activationline->special = 0;
-				DPrintf(DMSG_SPAMMY, "Cleared line special on line %d\n", (int)(activationline - lines));
+				DPrintf(DMSG_SPAMMY, "Cleared line special on line %d\n", activationline->Index());
 			}
 			break;
 
@@ -8307,32 +8306,33 @@ scriptwait:
 
 		case PCD_SETLINEBLOCKING:
 			{
-				int line;
+				int lineno;
 
 				FLineIdIterator itr(STACK(2));
-				while ((line = itr.Next()) >= 0)
+				while ((lineno = itr.Next()) >= 0)
 				{
+					auto &line = level.lines[lineno];
 					switch (STACK(1))
 					{
 					case BLOCK_NOTHING:
-						lines[line].flags &= ~(ML_BLOCKING|ML_BLOCKEVERYTHING|ML_RAILING|ML_BLOCK_PLAYERS);
+						line.flags &= ~(ML_BLOCKING|ML_BLOCKEVERYTHING|ML_RAILING|ML_BLOCK_PLAYERS);
 						break;
 					case BLOCK_CREATURES:
 					default:
-						lines[line].flags &= ~(ML_BLOCKEVERYTHING|ML_RAILING|ML_BLOCK_PLAYERS);
-						lines[line].flags |= ML_BLOCKING;
+						line.flags &= ~(ML_BLOCKEVERYTHING|ML_RAILING|ML_BLOCK_PLAYERS);
+						line.flags |= ML_BLOCKING;
 						break;
 					case BLOCK_EVERYTHING:
-						lines[line].flags &= ~(ML_RAILING|ML_BLOCK_PLAYERS);
-						lines[line].flags |= ML_BLOCKING|ML_BLOCKEVERYTHING;
+						line.flags &= ~(ML_RAILING|ML_BLOCK_PLAYERS);
+						line.flags |= ML_BLOCKING|ML_BLOCKEVERYTHING;
 						break;
 					case BLOCK_RAILING:
-						lines[line].flags &= ~(ML_BLOCKEVERYTHING|ML_BLOCK_PLAYERS);
-						lines[line].flags |= ML_RAILING|ML_BLOCKING;
+						line.flags &= ~(ML_BLOCKEVERYTHING|ML_BLOCK_PLAYERS);
+						line.flags |= ML_RAILING|ML_BLOCKING;
 						break;
 					case BLOCK_PLAYERS:
-						lines[line].flags &= ~(ML_BLOCKEVERYTHING|ML_BLOCKING|ML_RAILING);
-						lines[line].flags |= ML_BLOCK_PLAYERS;
+						line.flags &= ~(ML_BLOCKEVERYTHING|ML_BLOCKING|ML_RAILING);
+						line.flags |= ML_BLOCK_PLAYERS;
 						break;
 					}
 				}
@@ -8349,9 +8349,9 @@ scriptwait:
 				while ((line = itr.Next()) >= 0)
 				{
 					if (STACK(1))
-						lines[line].flags |= ML_BLOCKMONSTERS;
+						level.lines[line].flags |= ML_BLOCKMONSTERS;
 					else
-						lines[line].flags &= ~ML_BLOCKMONSTERS;
+						level.lines[line].flags &= ~ML_BLOCKMONSTERS;
 				}
 
 				sp -= 2;
@@ -8374,7 +8374,7 @@ scriptwait:
 				FLineIdIterator itr(STACK(7));
 				while ((linenum = itr.Next()) >= 0)
 				{
-					line_t *line = &lines[linenum];
+					line_t *line = &level.lines[linenum];
 					line->special = specnum;
 					line->args[0] = arg0;
 					line->args[1] = STACK(4);
diff --git a/src/p_actionfunctions.cpp b/src/p_actionfunctions.cpp
index f4b2f8103..b90f656c1 100644
--- a/src/p_actionfunctions.cpp
+++ b/src/p_actionfunctions.cpp
@@ -80,6 +80,7 @@
 #include "math/cmath.h"
 #include "a_armor.h"
 #include "a_health.h"
+#include "g_levellocals.h"
 
 AActor *SingleActorFromTID(int tid, AActor *defactor);
 
diff --git a/src/p_buildmap.cpp b/src/p_buildmap.cpp
index 99f3fb638..3a1943fc8 100644
--- a/src/p_buildmap.cpp
+++ b/src/p_buildmap.cpp
@@ -19,6 +19,7 @@
 #include "gi.h"
 #include "p_spec.h"
 
+#if 0
 // MACROS ------------------------------------------------------------------
 
 //#define SHADE2LIGHT(s) (160-2*(s))
@@ -487,7 +488,7 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 	// Setting numvertexes to the same as numwalls is overly conservative,
 	// but the extra vertices will be removed during the BSP building pass.
 	numsides = numvertexes = numwalls;
-	numlines = 0;
+	int numlines = 0;
 
 	sides = new side_t[numsides];
 	memset (sides, 0, numsides*sizeof(side_t));
@@ -562,8 +563,8 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 	}
 
 	// Set line properties that Doom doesn't store per-sidedef
-	lines = new line_t[numlines];
-	memset (lines, 0, numlines*sizeof(line_t));
+	level.lines.Alloc(numlines);
+	memset (&level.lines[0], 0, numlines*sizeof(line_t));
 
 	for (i = 0, j = -1; i < numwalls; ++i)
 	{
@@ -573,6 +574,7 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 		}
 
 		j = int(intptr_t(sides[i].linedef));
+		auto &lines = level.lines;
 		lines[j].sidedef[0] = (side_t*)(intptr_t)i;
 		lines[j].sidedef[1] = (side_t*)(intptr_t)walls[i].nextwall;
 		lines[j].v1 = FindVertex (walls[i].x, walls[i].y);
@@ -654,8 +656,8 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 			slope.z[0] = slope.z[1] = slope.z[2] = -bsec->ceilingZ;
 			CalcPlane (slope, sec.ceilingplane);
 		}
-		int linenum = int(intptr_t(sides[bsec->wallptr].linedef));
-		int sidenum = int(intptr_t(lines[linenum].sidedef[1]));
+		int linenum = sides[bsec->wallptr].linedef->Index();
+		int sidenum = int(intptr_t(level.lines[linenum].sidedef[1] - sides));
 		if (bsec->floorstat & 64)
 		{ // floor is aligned to first wall
 			P_AlignFlat (linenum, sidenum == bsec->wallptr, 0);
@@ -667,8 +669,8 @@ static void LoadWalls (walltype *walls, int numwalls, sectortype *bsec)
 	}
 	for (i = 0; i < numlines; i++)
 	{
-		intptr_t front = intptr_t(lines[i].sidedef[0]);
-		intptr_t back = intptr_t(lines[i].sidedef[1]);
+		intptr_t front = intptr_t(level.lines[i].sidedef[0]-sides);
+		intptr_t back = intptr_t(level.lines[i].sidedef[1]-sides);
 		lines[i].sidedef[0] = front >= 0 ? &sides[front] : NULL;
 		lines[i].sidedef[1] = back >= 0 ? &sides[back] : NULL;
 	}
@@ -851,6 +853,7 @@ static void Decrypt (void *to_, const void *from_, int len, int key)
 	}
 }
 
+#endif
 //==========================================================================
 //
 // Just an actor to make the Build sprites show up. It doesn't do anything
@@ -892,3 +895,4 @@ void ACustomSprite::BeginPlay ()
 	// set face/wall/floor flags
 	renderflags |= ActorRenderFlags::FromInt (((cstat >> 4) & 3) << 12);
 }
+
diff --git a/src/p_ceiling.cpp b/src/p_ceiling.cpp
index 79fd29591..7bf1f9099 100644
--- a/src/p_ceiling.cpp
+++ b/src/p_ceiling.cpp
@@ -31,6 +31,7 @@
 #include "gi.h"
 #include "serializer.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 //============================================================================
 //
diff --git a/src/p_conversation.cpp b/src/p_conversation.cpp
index 5fd21e73b..4f7f2fea7 100644
--- a/src/p_conversation.cpp
+++ b/src/p_conversation.cpp
@@ -60,6 +60,7 @@
 #include "r_utility.h"
 #include "p_local.h"
 #include "menu/menu.h"
+#include "g_levellocals.h"
 
 // The conversations as they exist inside a SCRIPTxx lump.
 struct Response
diff --git a/src/p_doors.cpp b/src/p_doors.cpp
index 1490647fc..3101be1c7 100644
--- a/src/p_doors.cpp
+++ b/src/p_doors.cpp
@@ -38,6 +38,7 @@
 #include "serializer.h"
 #include "d_player.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 //============================================================================
 //
diff --git a/src/p_effect.cpp b/src/p_effect.cpp
index 107759427..e0679338d 100644
--- a/src/p_effect.cpp
+++ b/src/p_effect.cpp
@@ -53,6 +53,7 @@
 #include "colormatcher.h"
 #include "d_player.h"
 #include "r_utility.h"
+#include "g_levellocals.h"
 
 CVAR (Int, cl_rockettrails, 1, CVAR_ARCHIVE);
 CVAR (Bool, r_rail_smartspiral, 0, CVAR_ARCHIVE);
@@ -272,7 +273,7 @@ void P_ThinkParticles ()
 		auto oldtrans = particle->alpha;
 		particle->alpha -= particle->fadestep;
 		particle->size += particle->sizestep;
-		if (oldtrans < particle->alpha || --particle->ttl <= 0 || (particle->size <= 0))
+		if (particle->alpha <= 0 || oldtrans < particle->alpha || --particle->ttl <= 0 || (particle->size <= 0))
 		{ // The particle has expired, so free it
 			memset (particle, 0, sizeof(particle_t));
 			if (prev)
diff --git a/src/p_enemy.cpp b/src/p_enemy.cpp
index a3d48a7ac..ac4e0f04b 100644
--- a/src/p_enemy.cpp
+++ b/src/p_enemy.cpp
@@ -52,6 +52,7 @@
 #include "p_checkposition.h"
 #include "math/cmath.h"
 #include "a_ammo.h"
+#include "g_levellocals.h"
 
 #include "gi.h"
 
diff --git a/src/p_floor.cpp b/src/p_floor.cpp
index dbe3792da..48c73f131 100644
--- a/src/p_floor.cpp
+++ b/src/p_floor.cpp
@@ -32,6 +32,7 @@
 #include "p_3dmidtex.h"
 #include "p_spec.h"
 #include "r_data/r_interpolate.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/p_glnodes.cpp b/src/p_glnodes.cpp
index 26e341aab..35f9f4502 100644
--- a/src/p_glnodes.cpp
+++ b/src/p_glnodes.cpp
@@ -67,6 +67,7 @@
 #include "m_misc.h"
 #include "r_utility.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 void P_GetPolySpots (MapData * lump, TArray<FNodeBuilder::FPolyStart> &spots, TArray<FNodeBuilder::FPolyStart> &anchors);
 
@@ -129,6 +130,7 @@ struct gl5_mapnode_t
 
 static int CheckForMissingSegs()
 {
+	auto numsides = level.sides.Size();
 	double *added_seglen = new double[numsides];
 	int missing = 0;
 
@@ -141,13 +143,13 @@ static int CheckForMissingSegs()
 		{
 			// check all the segs and calculate the length they occupy on their sidedef
 			DVector2 vec1(seg->v2->fX() - seg->v1->fX(), seg->v2->fY() - seg->v1->fY());
-			added_seglen[seg->sidedef - sides] += vec1.Length();
+			added_seglen[seg->sidedef->Index()] += vec1.Length();
 		}
 	}
 
-	for(int i=0;i<numsides;i++)
+	for(unsigned i=0;i<numsides;i++)
 	{
-		double linelen = sides[i].linedef->Delta().Length();
+		double linelen = level.sides[i].linedef->Delta().Length();
 		missing += (added_seglen[i] < linelen - 1.);
 	}
 
@@ -222,7 +224,7 @@ static bool LoadGLVertexes(FileReader * lump)
 	BYTE *gldata;
 	int                 i;
 
-	firstglvertex = numvertexes;
+	firstglvertex = level.vertexes.Size();
 	
 	int gllen=lump->GetLength();
 
@@ -247,23 +249,23 @@ static bool LoadGLVertexes(FileReader * lump)
 	}
 	else format5=false;
 
-	mapglvertex_t*	mgl;
+	mapglvertex_t*	mgl = (mapglvertex_t *)(gldata + GL_VERT_OFFSET);
+	unsigned numvertexes = firstglvertex +  (gllen - GL_VERT_OFFSET)/sizeof(mapglvertex_t);
 
-	vertex_t * oldvertexes = vertexes;
-	numvertexes += (gllen - GL_VERT_OFFSET)/sizeof(mapglvertex_t);
-	vertexes	 = new vertex_t[numvertexes];
-	mgl			 = (mapglvertex_t *) (gldata + GL_VERT_OFFSET);	
+	TStaticArray<vertex_t> oldvertexes = std::move(level.vertexes);
+	level.vertexes.Alloc(numvertexes);
 
-	memcpy(vertexes, oldvertexes, firstglvertex * sizeof(vertex_t));
-	for(i=0;i<numlines;i++)
+	memcpy(&level.vertexes[0], &oldvertexes[0], firstglvertex * sizeof(vertex_t));
+	for(auto &line : level.lines)
 	{
-		lines[i].v1 = vertexes + (lines[i].v1 - oldvertexes);
-		lines[i].v2 = vertexes + (lines[i].v2 - oldvertexes);
+		// Remap vertex pointers in linedefs
+		line.v1 = &level.vertexes[line.v1 - &oldvertexes[0]];
+		line.v2 = &level.vertexes[line.v2 - &oldvertexes[0]];
 	}
 
-	for (i = firstglvertex; i < numvertexes; i++)
+	for (i = firstglvertex; i < (int)numvertexes; i++)
 	{
-		vertexes[i].set(LittleLong(mgl->x)/65536., LittleLong(mgl->y)/65536.);
+		level.vertexes[i].set(LittleLong(mgl->x)/65536., LittleLong(mgl->y)/65536.);
 		mgl++;
 	}
 	delete[] gldata;
@@ -317,18 +319,16 @@ static bool LoadGLSegs(FileReader * lump)
 			numsegs/=sizeof(glseg_t);
 			segs = new seg_t[numsegs];
 			memset(segs,0,sizeof(seg_t)*numsegs);
-			glsegextras = new glsegextra_t[numsegs];
 			
 			glseg_t * ml = (glseg_t*)data;
 			for(i = 0; i < numsegs; i++)
 			{							// check for gl-vertices
-				segs[i].v1 = &vertexes[checkGLVertex(LittleShort(ml->v1))];
-				segs[i].v2 = &vertexes[checkGLVertex(LittleShort(ml->v2))];
-				
-				glsegextras[i].PartnerSeg = ml->partner == 0xFFFF ? DWORD_MAX : LittleShort(ml->partner);
+				segs[i].v1 = &level.vertexes[checkGLVertex(LittleShort(ml->v1))];
+				segs[i].v2 = &level.vertexes[checkGLVertex(LittleShort(ml->v2))];
+				segs[i].PartnerSeg = ml->partner == 0xFFFF ? nullptr : &segs[LittleShort(ml->partner)];
 				if(ml->linedef != 0xffff)
 				{
-					ldef = &lines[LittleShort(ml->linedef)];
+					ldef = &level.lines[LittleShort(ml->linedef)];
 					segs[i].linedef = ldef;
 	
 					
@@ -370,19 +370,17 @@ static bool LoadGLSegs(FileReader * lump)
 			numsegs/=sizeof(glseg3_t);
 			segs = new seg_t[numsegs];
 			memset(segs,0,sizeof(seg_t)*numsegs);
-			glsegextras = new glsegextra_t[numsegs];
 			
 			glseg3_t * ml = (glseg3_t*)(data+ (format5? 0:4));
 			for(i = 0; i < numsegs; i++)
 			{							// check for gl-vertices
-				segs[i].v1 = &vertexes[checkGLVertex3(LittleLong(ml->v1))];
-				segs[i].v2 = &vertexes[checkGLVertex3(LittleLong(ml->v2))];
-				
-				glsegextras[i].PartnerSeg = LittleLong(ml->partner);
+				segs[i].v1 = &level.vertexes[checkGLVertex3(LittleLong(ml->v1))];
+				segs[i].v2 = &level.vertexes[checkGLVertex3(LittleLong(ml->v2))];
+				segs[i].PartnerSeg = LittleLong(ml->partner) == 0xffffffffu? nullptr : &segs[LittleLong(ml->partner)];
 	
 				if(ml->linedef != 0xffff) // skip minisegs 
 				{
-					ldef = &lines[LittleLong(ml->linedef)];
+					ldef = &level.lines[LittleLong(ml->linedef)];
 					segs[i].linedef = ldef;
 	
 					
@@ -1000,18 +998,18 @@ bool P_CheckNodes(MapData * map, bool rebuilt, int buildtime)
 			P_GetPolySpots (map, polyspots, anchors);
 			FNodeBuilder::FLevel leveldata =
 			{
-				vertexes, numvertexes,
-				sides, numsides,
-				lines, numlines,
+				&level.vertexes[0], (int)level.vertexes.Size(),
+				&level.sides[0], (int)level.sides.Size(),
+				&level.lines[0], (int)level.lines.Size(),
 				0, 0, 0, 0
 			};
 			leveldata.FindMapBounds ();
 			FNodeBuilder builder (leveldata, polyspots, anchors, true);
-			delete[] vertexes;
+			
 			builder.Extract (nodes, numnodes,
-				segs, glsegextras, numsegs,
+				segs, numsegs,
 				subsectors, numsubsectors,
-				vertexes, numvertexes);
+				level.vertexes);
 			endTime = I_FPSTime ();
 			DPrintf (DMSG_NOTIFY, "BSP generation took %.3f sec (%d segs)\n", (endTime - startTime) * 0.001, numsegs);
 			buildtime = endTime - startTime;
@@ -1093,11 +1091,11 @@ static void CreateCachedNodes(MapData *map)
 	MemFile ZNodes;
 
 	WriteLong(ZNodes, 0);
-	WriteLong(ZNodes, numvertexes);
-	for(int i=0;i<numvertexes;i++)
+	WriteLong(ZNodes, level.vertexes.Size());
+	for(auto &vert : level.vertexes)
 	{
-		WriteLong(ZNodes, vertexes[i].fixX());
-		WriteLong(ZNodes, vertexes[i].fixY());
+		WriteLong(ZNodes, vert.fixX());
+		WriteLong(ZNodes, vert.fixY());
 	}
 
 	WriteLong(ZNodes, numsubsectors);
@@ -1109,12 +1107,11 @@ static void CreateCachedNodes(MapData *map)
 	WriteLong(ZNodes, numsegs);
 	for(int i=0;i<numsegs;i++)
 	{
-		WriteLong(ZNodes, DWORD(segs[i].v1 - vertexes));
-		if (glsegextras != NULL) WriteLong(ZNodes, DWORD(glsegextras[i].PartnerSeg));
-		else WriteLong(ZNodes, 0);
+		WriteLong(ZNodes, segs[i].v1->Index());
+		WriteLong(ZNodes, segs[i].PartnerSeg == nullptr? 0xffffffffu : DWORD(segs[i].PartnerSeg - segs));
 		if (segs[i].linedef)
 		{
-			WriteLong(ZNodes, DWORD(segs[i].linedef - lines));
+			WriteLong(ZNodes, DWORD(segs[i].linedef->Index()));
 			WriteByte(ZNodes, segs[i].sidedef == segs[i].linedef->sidedef[0]? 0:1);
 		}
 		else
@@ -1156,7 +1153,7 @@ static void CreateCachedNodes(MapData *map)
 
 	uLongf outlen = ZNodes.Size();
 	BYTE *compressed;
-	int offset = numlines * 8 + 12 + 16;
+	int offset = level.lines.Size() * 8 + 12 + 16;
 	int r;
 	do
 	{
@@ -1171,13 +1168,13 @@ static void CreateCachedNodes(MapData *map)
 	while (r == Z_BUF_ERROR);
 
 	memcpy(compressed, "CACH", 4);
-	DWORD len = LittleLong(numlines);
+	DWORD len = LittleLong(level.lines.Size());
 	memcpy(compressed+4, &len, 4);
 	map->GetChecksum(compressed+8);
-	for(int i=0;i<numlines;i++)
+	for (unsigned i = 0; i < level.lines.Size(); i++)
 	{
-		DWORD ndx[2] = {LittleLong(DWORD(lines[i].v1 - vertexes)), LittleLong(DWORD(lines[i].v2 - vertexes)) };
-		memcpy(compressed+8+16+8*i, ndx, 8);
+		DWORD ndx[2] = { LittleLong(DWORD(level.lines[i].v1->Index())), LittleLong(DWORD(level.lines[i].v2->Index())) };
+		memcpy(compressed + 8 + 16 + 8 * i, ndx, 8);
 	}
 	memcpy(compressed + offset - 4, "ZGL3", 4);
 
@@ -1219,7 +1216,7 @@ static bool CheckCachedNodes(MapData *map)
 
 	if (fread(&numlin, 4, 1, f) != 1) goto errorout; 
 	numlin = LittleLong(numlin);
-	if ((int)numlin != numlines) goto errorout;
+	if (numlin != level.lines.Size()) goto errorout;
 
 	if (fread(md5, 1, 16, f) != 16) goto errorout;
 	map->GetChecksum(md5map);
@@ -1261,10 +1258,11 @@ static bool CheckCachedNodes(MapData *map)
 		goto errorout;
 	}
 
-	for(int i=0;i<numlines;i++)
+	for(auto &line : level.lines)
 	{
-		lines[i].v1 = &vertexes[LittleLong(verts[i*2])];
-		lines[i].v2 = &vertexes[LittleLong(verts[i*2+1])];
+		int i = line.Index();
+		line.v1 = &level.vertexes[LittleLong(verts[i*2])];
+		line.v2 = &level.vertexes[LittleLong(verts[i*2+1])];
 	}
 	delete [] verts;
 
@@ -1437,40 +1435,32 @@ void P_SetRenderSector()
 #endif
 
 	// Check for incorrect partner seg info so that the following code does not crash.
-	if (glsegextras == NULL)
+
+	for (i = 0; i < numsegs; i++)
 	{
-		// This can be normal nodes, mistakenly identified as GL nodes so we must fill
-		// in the missing pieces differently.
-
-		for (i = 0; i < numsubsectors; i++)
+		auto p = segs[i].PartnerSeg;
+		if (p != nullptr)
 		{
-			ss = &subsectors[i];
-			ss->render_sector = ss->sector;
-		}
-		return;
-	}
+			int partner = (int)(p - segs);
 
-	for(i=0;i<numsegs;i++)
-	{
-		int partner = (int)glsegextras[i].PartnerSeg;
+			if (partner < 0 || partner >= numsegs)
+			{
+				segs[i].PartnerSeg = nullptr;
+			}
 
-		if (partner<0 || partner>=numsegs/*eh? || &segs[partner]!=glsegextras[i].PartnerSeg*/)
-		{
-			glsegextras[i].PartnerSeg=DWORD_MAX;
+			// glbsp creates such incorrect references for Strife.
+			if (segs[i].linedef && segs[i].PartnerSeg != nullptr && !segs[i].PartnerSeg->linedef)
+			{
+				segs[i].PartnerSeg = segs[i].PartnerSeg->PartnerSeg = nullptr;
+			}
 		}
 
-		// glbsp creates such incorrect references for Strife.
-		if (segs[i].linedef && glsegextras[i].PartnerSeg != DWORD_MAX && !segs[glsegextras[i].PartnerSeg].linedef)
+		for (i = 0; i < numsegs; i++)
 		{
-			glsegextras[i].PartnerSeg = glsegextras[glsegextras[i].PartnerSeg].PartnerSeg = DWORD_MAX;
-		}
-	}
-
-	for(i=0;i<numsegs;i++)
-	{
-		if (glsegextras[i].PartnerSeg != DWORD_MAX && glsegextras[glsegextras[i].PartnerSeg].PartnerSeg!=(DWORD)i)
-		{
-			glsegextras[i].PartnerSeg=DWORD_MAX;
+			if (segs[i].PartnerSeg != nullptr && segs[i].PartnerSeg->PartnerSeg != &segs[i])
+			{
+				segs[i].PartnerSeg = nullptr;
+			}
 		}
 	}
 
@@ -1498,7 +1488,7 @@ void P_SetRenderSector()
 		seg = ss->firstline;
 		for(j=0; j<ss->numlines; j++)
 		{
-			if(seg->sidedef && (glsegextras[seg - segs].PartnerSeg == DWORD_MAX || seg->sidedef->sector!=segs[glsegextras[seg - segs].PartnerSeg].sidedef->sector))
+			if(seg->sidedef && (seg->PartnerSeg == nullptr || seg->sidedef->sector!=seg->PartnerSeg->sidedef->sector))
 			{
 				ss->render_sector = seg->sidedef->sector;
 				break;
@@ -1522,15 +1512,14 @@ void P_SetRenderSector()
 			
 			for(j=0; j<ss->numlines; j++)
 			{
-				DWORD partner = glsegextras[seg - segs].PartnerSeg;
-				if (partner != DWORD_MAX && glsegextras[partner].Subsector)
+				if (seg->PartnerSeg != nullptr && seg->PartnerSeg->Subsector)
 				{
-					sector_t * backsec = glsegextras[partner].Subsector->render_sector;
+					sector_t * backsec = seg->PartnerSeg->Subsector->render_sector;
 					if (backsec)
 					{
-						ss->render_sector=backsec;
+						ss->render_sector = backsec;
 						undetermined.Delete(i);
-						deleted=1;
+						deleted = 1;
 						break;
 					}
 				}
diff --git a/src/p_interaction.cpp b/src/p_interaction.cpp
index 9aa178e64..b6ffcb699 100644
--- a/src/p_interaction.cpp
+++ b/src/p_interaction.cpp
@@ -60,6 +60,7 @@
 #include "a_morph.h"
 #include "virtual.h"
 #include "a_health.h"
+#include "g_levellocals.h"
 
 static FRandom pr_obituary ("Obituary");
 static FRandom pr_botrespawn ("BotRespawn");
diff --git a/src/p_lights.cpp b/src/p_lights.cpp
index d9fc19c79..5442809e4 100644
--- a/src/p_lights.cpp
+++ b/src/p_lights.cpp
@@ -32,6 +32,7 @@
 #include "p_lnspec.h"
 #include "doomstat.h"
 #include "p_maputl.h"
+#include "g_levellocals.h"
 
 // State.
 #include "r_state.h"
diff --git a/src/p_linkedsectors.cpp b/src/p_linkedsectors.cpp
index 8a0cc9ca0..0dd29c10e 100644
--- a/src/p_linkedsectors.cpp
+++ b/src/p_linkedsectors.cpp
@@ -37,6 +37,7 @@
 #include "p_local.h"
 #include "p_lnspec.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 enum
 {
@@ -360,7 +361,7 @@ void P_AddSectorLinksByID(sector_t *control, int id, INTBOOL ceiling)
 	int line;
 	while ((line = itr.Next()) >= 0)
 	{
-		line_t *ld = &lines[line];
+		line_t *ld = &level.lines[line];
 
 		if (ld->special == Static_Init && ld->args[1] == Init_SectorLink)
 		{
diff --git a/src/p_lnspec.cpp b/src/p_lnspec.cpp
index c1e342de8..77682d1e3 100644
--- a/src/p_lnspec.cpp
+++ b/src/p_lnspec.cpp
@@ -61,6 +61,7 @@
 #include "r_data/colormaps.h"
 #include "fragglescript/t_fs.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 // Remaps EE sector change types to Generic_Floor values. According to the Eternity Wiki:
 /*
@@ -2604,7 +2605,7 @@ FUNC(LS_Line_SetTextureOffset)
 	int line;
 	while ((line = itr.Next()) >= 0)
 	{
-		side_t *side = lines[line].sidedef[arg3];
+		side_t *side = level.lines[line].sidedef[arg3];
 		if (side != NULL)
 		{
 
@@ -2659,7 +2660,7 @@ FUNC(LS_Line_SetTextureScale)
 	int line;
 	while ((line = itr.Next()) >= 0)
 	{
-		side_t *side = lines[line].sidedef[arg3];
+		side_t *side = level.lines[line].sidedef[arg3];
 		if (side != NULL)
 		{
 			if ((arg4&8)==0)
@@ -2733,7 +2734,7 @@ FUNC(LS_Line_SetBlocking)
 	int line;
 	while ((line = itr.Next()) >= 0)
 	{
-		lines[line].flags = (lines[line].flags & ~clearflags) | setflags;
+		level.lines[line].flags = (level.lines[line].flags & ~clearflags) | setflags;
 	}
 	return true;
 }
@@ -3028,14 +3029,14 @@ FUNC(LS_TranslucentLine)
 	int linenum;
 	while ((linenum = itr.Next()) >= 0)
 	{
-		lines[linenum].alpha = clamp(arg1, 0, 255) / 255.;
+		level.lines[linenum].alpha = clamp(arg1, 0, 255) / 255.;
 		if (arg2 == 0)
 		{
-			lines[linenum].flags &= ~ML_ADDTRANS;
+			level.lines[linenum].flags &= ~ML_ADDTRANS;
 		}
 		else if (arg2 == 1)
 		{
-			lines[linenum].flags |= ML_ADDTRANS;
+			level.lines[linenum].flags |= ML_ADDTRANS;
 		}
 		else
 		{
diff --git a/src/p_map.cpp b/src/p_map.cpp
index 7f6a47b66..d48fb4e5a 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -63,6 +63,7 @@
 #include "r_data/r_translate.h"
 #include "g_level.h"
 #include "r_sky.h"
+#include "g_levellocals.h"
 
 CVAR(Bool, cl_bloodsplats, true, CVAR_ARCHIVE)
 CVAR(Int, sv_smartaim, 0, CVAR_ARCHIVE | CVAR_SERVERINFO)
@@ -183,7 +184,7 @@ static bool PIT_FindFloorCeiling(FMultiBlockLinesIterator &mit, FMultiBlockLines
 	if (ffcf_verbose)
 	{
 		Printf("Hit line %d at position %f,%f, group %d\n",
-			int(ld - lines), cres.Position.X, cres.Position.Y, ld->frontsector->PortalGroup);
+			ld->Index(), cres.Position.X, cres.Position.Y, ld->frontsector->PortalGroup);
 	}
 
 	if (!ld->backsector)
@@ -3296,7 +3297,6 @@ bool FSlide::BounceTraverse(const DVector2 &start, const DVector2 &end)
 		}
 
 		li = in->d.line;
-		assert(((size_t)li - (size_t)lines) % sizeof(line_t) == 0);
 		if (li->flags & ML_BLOCKEVERYTHING)
 		{
 			goto bounceblocking;
@@ -3907,7 +3907,7 @@ struct aim_t
 				int frontflag = P_PointOnLineSidePrecise(startpos, li);
 
 				if (aimdebug)
-					Printf("Found line %d: ___toppitch = %f, ___bottompitch = %f\n", int(li - lines), toppitch.Degrees, bottompitch.Degrees);
+					Printf("Found line %d: toppitch = %f, bottompitch = %f\n", li->Index(), toppitch.Degrees, bottompitch.Degrees);
 
 				if (li->isLinePortal() && frontflag == 0)
 				{
@@ -3951,7 +3951,7 @@ struct aim_t
 					return;
 
 				if (aimdebug)
-					Printf("After line %d: toppitch = %f, bottompitch = %f, planestocheck = %d\n", int(li - lines), toppitch.Degrees, bottompitch.Degrees, planestocheck);
+					Printf("After line %d: toppitch = %f, bottompitch = %f, planestocheck = %d\n", li->Index(), toppitch.Degrees, bottompitch.Degrees, planestocheck);
 
 				sector_t *entersec = frontflag ? li->frontsector : li->backsector;
 				sector_t *exitsec = frontflag ? li->backsector : li->frontsector;
diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index d4ac79ce7..e6b2aebea 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -44,6 +44,7 @@
 #include "r_state.h"
 #include "templates.h"
 #include "po_man.h"
+#include "g_levellocals.h"
 
 sector_t *P_PointInSectorBuggy(double x, double y);
 int P_VanillaPointOnDivlineSide(double x, double y, const divline_t* line);
@@ -330,7 +331,7 @@ bool AActor::FixMapthingPos()
 
 		for (list = blockmaplump + blockmap[blocky*bmapwidth + blockx] + 1; *list != -1; ++list)
 		{
-			line_t *ldef = &lines[*list];
+			line_t *ldef = &level.lines[*list];
 
 			if (ldef->frontsector == ldef->backsector)
 			{ // Skip two-sided lines inside a single sector
@@ -367,10 +368,10 @@ bool AActor::FixMapthingPos()
 
 			if (distance < radius)
 			{
-				DPrintf(DMSG_NOTIFY, "%s at (%f,%f) lies on %s line %td, distance = %f\n",
+				DPrintf(DMSG_NOTIFY, "%s at (%f,%f) lies on %s line %d, distance = %f\n",
 					this->GetClass()->TypeName.GetChars(), X(), Y(),
 					ldef->Delta().X == 0 ? "vertical" : ldef->Delta().Y == 0 ? "horizontal" : "diagonal",
-					ldef - lines, distance);
+					ldef->Index(), distance);
 				DAngle ang = ldef->Delta().Angle();
 				if (ldef->backsector != NULL && ldef->backsector == secstart)
 				{
@@ -709,7 +710,7 @@ line_t *FBlockLinesIterator::Next()
 		{
 			while (*list != -1)
 			{
-				line_t *ld = &lines[*list];
+				line_t *ld = &level.lines[*list];
 
 				list++;
 				if (ld->validcount != validcount)
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 3bdf3718d..d5ec020a0 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -72,6 +72,7 @@
 #include "a_armor.h"
 #include "a_ammo.h"
 #include "a_health.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -7539,6 +7540,22 @@ DEFINE_ACTION_FUNCTION(AActor, A_RestoreSpecialPosition)
 	return 0;
 }
 
+double AActor::GetBobOffset(double ticfrac) const
+{
+	if (!(flags2 & MF2_FLOATBOB))
+	{
+		return 0;
+	}
+	return BobSin(FloatBobPhase + level.maptime + ticfrac);
+}
+
+DEFINE_ACTION_FUNCTION(AActor, GetBobOffset)
+{
+	PARAM_SELF_PROLOGUE(AActor);
+	PARAM_FLOAT_DEF(frac);
+	ACTION_RETURN_FLOAT(self->GetBobOffset(frac));
+}
+
 
 
 
@@ -7639,13 +7656,6 @@ DEFINE_ACTION_FUNCTION(AActor, GetDefaultByType)
 	ACTION_RETURN_OBJECT(cls == nullptr? nullptr : GetDefaultByType(cls));
 }
 
-DEFINE_ACTION_FUNCTION(AActor, GetBobOffset)
-{
-	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_FLOAT_DEF(frac);
-	ACTION_RETURN_FLOAT(self->GetBobOffset(frac));
-}
-
 // This combines all 3 variations of the internal function
 DEFINE_ACTION_FUNCTION(AActor, VelFromAngle)
 {
diff --git a/src/p_pillar.cpp b/src/p_pillar.cpp
index d4682e570..d603edc8a 100644
--- a/src/p_pillar.cpp
+++ b/src/p_pillar.cpp
@@ -39,6 +39,7 @@
 #include "s_sndseq.h"
 #include "serializer.h"
 #include "r_data/r_interpolate.h"
+#include "g_levellocals.h"
 
 IMPLEMENT_CLASS(DPillar, false, true)
 
diff --git a/src/p_plats.cpp b/src/p_plats.cpp
index 7bbf33b27..8dd82c024 100644
--- a/src/p_plats.cpp
+++ b/src/p_plats.cpp
@@ -32,6 +32,7 @@
 #include "gi.h"
 #include "serializer.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 static FRandom pr_doplat ("DoPlat");
 
diff --git a/src/p_pspr.cpp b/src/p_pspr.cpp
index c6f871ace..4d77bb645 100644
--- a/src/p_pspr.cpp
+++ b/src/p_pspr.cpp
@@ -30,6 +30,7 @@
 #include "serializer.h"
 #include "v_text.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 
 // MACROS ------------------------------------------------------------------
diff --git a/src/p_pusher.cpp b/src/p_pusher.cpp
index 8a4032b40..5190b5ced 100644
--- a/src/p_pusher.cpp
+++ b/src/p_pusher.cpp
@@ -32,6 +32,7 @@
 #include "p_maputl.h"
 #include "p_local.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 
 CVAR(Bool, var_pushers, true, CVAR_SERVERINFO);
 
@@ -358,11 +359,10 @@ AActor *P_GetPushThing (int s)
 
 void P_SpawnPushers ()
 {
-	int i;
-	line_t *l = lines;
+	line_t *l = &level.lines[0];
 	int s;
 
-	for (i = 0; i < numlines; i++, l++)
+	for (unsigned i = 0; i < level.lines.Size(); i++, l++)
 	{
 		switch (l->special)
 		{
diff --git a/src/p_saveg.cpp b/src/p_saveg.cpp
index 5f9aeec42..227fc91fd 100644
--- a/src/p_saveg.cpp
+++ b/src/p_saveg.cpp
@@ -62,6 +62,11 @@
 #include "r_sky.h"
 #include "r_renderer.h"
 #include "serializer.h"
+#include "g_levellocals.h"
+
+static TStaticArray<sector_t>	loadsectors;
+static TStaticArray<line_t>		loadlines;
+static TStaticArray<side_t>		loadsides;
 
 
 //==========================================================================
@@ -353,6 +358,7 @@ FSerializer &Serialize(FSerializer &arc, const char *key, subsector_t *&ss, subs
 			str = &encoded[0];
 			if (arc.BeginArray(key))
 			{
+				auto numvertexes = level.vertexes.Size();
 				arc(nullptr, numvertexes)
 					(nullptr, numsubsectors)
 					.StringPtr(nullptr, str)
@@ -371,7 +377,7 @@ FSerializer &Serialize(FSerializer &arc, const char *key, subsector_t *&ss, subs
 				.StringPtr(nullptr, str)
 				.EndArray();
 
-			if (num_verts == numvertexes && num_subs == numsubsectors && hasglnodes)
+			if (num_verts == level.vertexes.Size() && num_subs == numsubsectors && hasglnodes)
 			{
 				success = true;
 				int sub = 0;
@@ -898,8 +904,8 @@ void G_SerializeLevel(FSerializer &arc, bool hubload)
 		// deep down in the deserializer or just a crash if the few insufficient safeguards were not triggered.
 		BYTE chk[16] = { 0 };
 		arc.Array("checksum", chk, 16);
-		if (arc.GetSize("linedefs") != (unsigned)numlines ||
-			arc.GetSize("sidedefs") != (unsigned)numsides ||
+		if (arc.GetSize("linedefs") != level.lines.Size() ||
+			arc.GetSize("sidedefs") != level.sides.Size() ||
 			arc.GetSize("sectors") != level.sectors.Size() ||
 			arc.GetSize("polyobjs") != (unsigned)po_NumPolyobjs ||
 			memcmp(chk, level.md5, 16))
@@ -952,8 +958,8 @@ void G_SerializeLevel(FSerializer &arc, bool hubload)
 
 	FBehavior::StaticSerializeModuleStates(arc);
 	// The order here is important: First world state, then portal state, then thinkers, and last polyobjects.
-	arc.Array("linedefs", lines, &loadlines[0], numlines);
-	arc.Array("sidedefs", sides, &loadsides[0], numsides);
+	arc.Array("linedefs", &level.lines[0], &loadlines[0], level.lines.Size());
+	arc.Array("sidedefs", &level.sides[0], &loadsides[0], level.sides.Size());
 	arc.Array("sectors", &level.sectors[0], &loadsectors[0], level.sectors.Size());
 	arc("zones", Zones);
 	arc("lineportals", linePortals);
@@ -988,4 +994,18 @@ void G_SerializeLevel(FSerializer &arc, bool hubload)
 
 }
 
+// Create a backup of the map data so the savegame code can toss out all fields that haven't changed in order to reduce processing time and file size.
 
+void P_BackupMapData()
+{
+	loadsectors = level.sectors;
+	loadlines = level.lines;
+	loadsides = level.sides;
+}
+
+void P_FreeMapDataBackup()
+{
+	loadsectors.Clear();
+	loadlines.Clear();
+	loadsides.Clear();
+}
\ No newline at end of file
diff --git a/src/p_saveg.h b/src/p_saveg.h
index 6c4c74f46..715fd6a19 100644
--- a/src/p_saveg.h
+++ b/src/p_saveg.h
@@ -46,4 +46,7 @@ void P_WriteACSDefereds (FSerializer &);
 
 void G_SerializeLevel(FSerializer &arc, bool hubLoad);
 
+void P_BackupMapData();
+void P_FreeMapDataBackup();
+
 #endif // __P_SAVEG_H__
diff --git a/src/p_scroll.cpp b/src/p_scroll.cpp
index 954b1ac36..403eb3087 100644
--- a/src/p_scroll.cpp
+++ b/src/p_scroll.cpp
@@ -29,6 +29,7 @@
 #include "serializer.h"
 #include "p_lnspec.h"
 #include "r_data/r_interpolate.h"
+#include "g_levellocals.h"
 
 //-----------------------------------------------------------------------------
 //
@@ -191,19 +192,19 @@ void DScroller::Tick ()
 		case EScroll::sc_side:					// killough 3/7/98: Scroll wall texture
 			if (m_Parts & EScrollPos::scw_top)
 			{
-				sides[m_Affectee].AddTextureXOffset(side_t::top, dx);
-				sides[m_Affectee].AddTextureYOffset(side_t::top, dy);
+				level.sides[m_Affectee].AddTextureXOffset(side_t::top, dx);
+				level.sides[m_Affectee].AddTextureYOffset(side_t::top, dy);
 			}
-			if (m_Parts & EScrollPos::scw_mid && (sides[m_Affectee].linedef->backsector == NULL ||
-				!(sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
+			if (m_Parts & EScrollPos::scw_mid && (level.sides[m_Affectee].linedef->backsector == NULL ||
+				!(level.sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
 			{
-				sides[m_Affectee].AddTextureXOffset(side_t::mid, dx);
-				sides[m_Affectee].AddTextureYOffset(side_t::mid, dy);
+				level.sides[m_Affectee].AddTextureXOffset(side_t::mid, dx);
+				level.sides[m_Affectee].AddTextureYOffset(side_t::mid, dy);
 			}
 			if (m_Parts & EScrollPos::scw_bottom)
 			{
-				sides[m_Affectee].AddTextureXOffset(side_t::bottom, dx);
-				sides[m_Affectee].AddTextureYOffset(side_t::bottom, dy);
+				level.sides[m_Affectee].AddTextureXOffset(side_t::bottom, dx);
+				level.sides[m_Affectee].AddTextureYOffset(side_t::bottom, dy);
 			}
 			break;
 
@@ -276,19 +277,19 @@ DScroller::DScroller (EScroll type, double dx, double dy,
 		break;
 
 	case EScroll::sc_side:
-		sides[affectee].Flags |= WALLF_NOAUTODECALS;
+		level.sides[affectee].Flags |= WALLF_NOAUTODECALS;
 		if (m_Parts & EScrollPos::scw_top)
 		{
-			m_Interpolations[0] = sides[m_Affectee].SetInterpolation(side_t::top);
+			m_Interpolations[0] = level.sides[m_Affectee].SetInterpolation(side_t::top);
 		}
-		if (m_Parts & EScrollPos::scw_mid && (sides[m_Affectee].linedef->backsector == NULL ||
-			!(sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
+		if (m_Parts & EScrollPos::scw_mid && (level.sides[m_Affectee].linedef->backsector == nullptr ||
+			!(level.sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
 		{
-			m_Interpolations[1] = sides[m_Affectee].SetInterpolation(side_t::mid);
+			m_Interpolations[1] = level.sides[m_Affectee].SetInterpolation(side_t::mid);
 		}
 		if (m_Parts & EScrollPos::scw_bottom)
 		{
-			m_Interpolations[2] = sides[m_Affectee].SetInterpolation(side_t::bottom);
+			m_Interpolations[2] = level.sides[m_Affectee].SetInterpolation(side_t::bottom);
 		}
 		break;
 
@@ -349,22 +350,22 @@ DScroller::DScroller (double dx, double dy, const line_t *l,
 	m_LastHeight = 0;
 	if ((m_Control = control) != -1)
 		m_LastHeight = level.sectors[control].CenterFloor() + level.sectors[control].CenterCeiling();
-	m_Affectee = int(l->sidedef[0] - sides);
-	sides[m_Affectee].Flags |= WALLF_NOAUTODECALS;
+	m_Affectee = l->sidedef[0]->Index();
+	level.sides[m_Affectee].Flags |= WALLF_NOAUTODECALS;
 	m_Interpolations[0] = m_Interpolations[1] = m_Interpolations[2] = NULL;
 
 	if (m_Parts & EScrollPos::scw_top)
 	{
-		m_Interpolations[0] = sides[m_Affectee].SetInterpolation(side_t::top);
+		m_Interpolations[0] = level.sides[m_Affectee].SetInterpolation(side_t::top);
 	}
-	if (m_Parts & EScrollPos::scw_mid && (sides[m_Affectee].linedef->backsector == NULL ||
-		!(sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
+	if (m_Parts & EScrollPos::scw_mid && (level.sides[m_Affectee].linedef->backsector == NULL ||
+		!(level.sides[m_Affectee].linedef->flags&ML_3DMIDTEX)))
 	{
-		m_Interpolations[1] = sides[m_Affectee].SetInterpolation(side_t::mid);
+		m_Interpolations[1] = level.sides[m_Affectee].SetInterpolation(side_t::mid);
 	}
 	if (m_Parts & EScrollPos::scw_bottom)
 	{
-		m_Interpolations[2] = sides[m_Affectee].SetInterpolation(side_t::bottom);
+		m_Interpolations[2] = level.sides[m_Affectee].SetInterpolation(side_t::bottom);
 	}
 }
 
@@ -380,24 +381,23 @@ DScroller::DScroller (double dx, double dy, const line_t *l,
 
 void P_SpawnScrollers(void)
 {
-	int i;
-	line_t *l = lines;
+	line_t *l = &level.lines[0];
 	TArray<int> copyscrollers;
 
-	for (i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		if (lines[i].special == Sector_CopyScroller)
+		if (line.special == Sector_CopyScroller)
 		{
 			// don't allow copying the scroller if the sector has the same tag as it would just duplicate it.
-			if (!tagManager.SectorHasTag(lines[i].frontsector, lines[i].args[0]))
+			if (!tagManager.SectorHasTag(line.frontsector, line.args[0]))
 			{
-				copyscrollers.Push(i);
+				copyscrollers.Push(line.Index());
 			}
-			lines[i].special = 0;
+			line.special = 0;
 		}
 	}
 
-	for (i = 0; i < numlines; i++, l++)
+	for (unsigned i = 0; i < level.lines.Size(); i++, l++)
 	{
 		double dx;	// direction and speed of scrolling
 		double dy;
@@ -474,7 +474,7 @@ void P_SpawnScrollers(void)
 			}
 			for (unsigned j = 0; j < copyscrollers.Size(); j++)
 			{
-				line_t *line = &lines[copyscrollers[j]];
+				line_t *line = &level.lines[copyscrollers[j]];
 
 				if (line->args[0] == l->args[0] && (line->args[1] & 1))
 				{
@@ -494,7 +494,7 @@ void P_SpawnScrollers(void)
 				}
 				for(unsigned j = 0;j < copyscrollers.Size(); j++)
 				{
-					line_t *line = &lines[copyscrollers[j]];
+					line_t *line = &level.lines[copyscrollers[j]];
 
 					if (line->args[0] == l->args[0] && (line->args[1] & 2))
 					{
@@ -512,7 +512,7 @@ void P_SpawnScrollers(void)
 				}
 				for(unsigned j = 0;j < copyscrollers.Size(); j++)
 				{
-					line_t *line = &lines[copyscrollers[j]];
+					line_t *line = &level.lines[copyscrollers[j]];
 
 					if (line->args[0] == l->args[0] && (line->args[1] & 4))
 					{
@@ -530,48 +530,48 @@ void P_SpawnScrollers(void)
 			while ((s = itr.Next()) >= 0)
 			{
 				if (s != i)
-					new DScroller(dx, dy, lines + s, control, accel);
+					new DScroller(dx, dy, &level.lines[s], control, accel);
 			}
 			break;
 		}
 
 		case Scroll_Texture_Offsets:
 			// killough 3/2/98: scroll according to sidedef offsets
-			s = int(lines[i].sidedef[0] - sides);
-			new DScroller (EScroll::sc_side, -sides[s].GetTextureXOffset(side_t::mid),
-				sides[s].GetTextureYOffset(side_t::mid), -1, s, accel, SCROLLTYPE(l->args[0]));
+			s = level.lines[i].sidedef[0]->Index();
+			new DScroller (EScroll::sc_side, -level.sides[s].GetTextureXOffset(side_t::mid),
+				level.sides[s].GetTextureYOffset(side_t::mid), -1, s, accel, SCROLLTYPE(l->args[0]));
 			break;
 
 		case Scroll_Texture_Left:
 			l->special = special;	// Restore the special, for compat_useblocking's benefit.
-			s = int(lines[i].sidedef[0] - sides);
+			s = level.lines[i].sidedef[0]->Index();
 			new DScroller (EScroll::sc_side, l->args[0] / 64., 0,
 						   -1, s, accel, SCROLLTYPE(l->args[1]));
 			break;
 
 		case Scroll_Texture_Right:
 			l->special = special;
-			s = int(lines[i].sidedef[0] - sides);
+			s = level.lines[i].sidedef[0]->Index();
 			new DScroller (EScroll::sc_side, -l->args[0] / 64., 0,
 						   -1, s, accel, SCROLLTYPE(l->args[1]));
 			break;
 
 		case Scroll_Texture_Up:
 			l->special = special;
-			s = int(lines[i].sidedef[0] - sides);
+			s = level.lines[i].sidedef[0]->Index();
 			new DScroller (EScroll::sc_side, 0, l->args[0] / 64.,
 						   -1, s, accel, SCROLLTYPE(l->args[1]));
 			break;
 
 		case Scroll_Texture_Down:
 			l->special = special;
-			s = int(lines[i].sidedef[0] - sides);
+			s = level.lines[i].sidedef[0]->Index();
 			new DScroller (EScroll::sc_side, 0, -l->args[0] / 64.,
 						   -1, s, accel, SCROLLTYPE(l->args[1]));
 			break;
 
 		case Scroll_Texture_Both:
-			s = int(lines[i].sidedef[0] - sides);
+			s = level.lines[i].sidedef[0]->Index();
 			if (l->args[0] == 0) {
 				dx = (l->args[1] - l->args[2]) / 64.;
 				dy = (l->args[4] - l->args[3]) / 64.;
@@ -608,8 +608,8 @@ void SetWallScroller (int id, int sidechoice, double dx, double dy, EScrollPos W
 		{
 			int wallnum = scroller->GetWallNum ();
 
-			if (wallnum >= 0 && tagManager.LineHasID(sides[wallnum].linedef, id) &&
-				int(sides[wallnum].linedef->sidedef[sidechoice] - sides) == wallnum &&
+			if (wallnum >= 0 && tagManager.LineHasID(level.sides[wallnum].linedef, id) &&
+				level.sides[wallnum].linedef->sidedef[sidechoice]->Index() == wallnum &&
 				Where == scroller->GetScrollParts())
 			{
 				scroller->Destroy ();
@@ -628,8 +628,8 @@ void SetWallScroller (int id, int sidechoice, double dx, double dy, EScrollPos W
 			while ( (collect.Obj = iterator.Next ()) )
 			{
 				if ((collect.RefNum = ((DScroller *)collect.Obj)->GetWallNum ()) != -1 &&
-					tagManager.LineHasID(sides[collect.RefNum].linedef, id) &&
-					int(sides[collect.RefNum].linedef->sidedef[sidechoice] - sides) == collect.RefNum &&
+					tagManager.LineHasID(level.sides[collect.RefNum].linedef, id) &&
+					level.sides[collect.RefNum].linedef->sidedef[sidechoice]->Index() == collect.RefNum &&
 					Where == ((DScroller *)collect.Obj)->GetScrollParts())
 				{
 					((DScroller *)collect.Obj)->SetRate (dx, dy);
@@ -645,9 +645,9 @@ void SetWallScroller (int id, int sidechoice, double dx, double dy, EScrollPos W
 		FLineIdIterator itr(id);
 		while ((linenum = itr.Next()) >= 0)
 		{
-			if (lines[linenum].sidedef[sidechoice] != NULL)
+			if (level.lines[linenum].sidedef[sidechoice] != NULL)
 			{
-				int sidenum = int(lines[linenum].sidedef[sidechoice] - sides);
+				int sidenum = level.lines[linenum].sidedef[sidechoice]->Index();
 				unsigned int i;
 				for (i = 0; i < numcollected; i++)
 				{
diff --git a/src/p_sectors.cpp b/src/p_sectors.cpp
index d4abcc534..c95f48d15 100644
--- a/src/p_sectors.cpp
+++ b/src/p_sectors.cpp
@@ -35,6 +35,7 @@
 #include "p_local.h"
 #include "r_sky.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 
 // [RH]
@@ -710,7 +711,7 @@ double sector_t::FindHighestFloorPoint (vertex_t **v) const
 	{
 		if (v != NULL)
 		{
-			if (Lines.Size() == 0) *v = &vertexes[0];
+			if (Lines.Size() == 0) *v = &level.vertexes[0];
 			else *v = Lines[0]->v1;
 		}
 		return -floorplane.fD();
@@ -759,7 +760,7 @@ double sector_t::FindLowestCeilingPoint (vertex_t **v) const
 	{
 		if (v != NULL)
 		{
-			if (Lines.Size() == 0) *v = &vertexes[0];
+			if (Lines.Size() == 0) *v = &level.vertexes[0];
 			else *v = Lines[0]->v1;
 		}
 		return ceilingplane.fD();
@@ -1772,6 +1773,205 @@ DEFINE_ACTION_FUNCTION(_Sector, NextLowestFloorAt)
 	 ACTION_RETURN_FLOAT(self->CenterCeiling());
  }
 
+ DEFINE_ACTION_FUNCTION(_Sector, Index)
+ {
+	PARAM_SELF_STRUCT_PROLOGUE(sector_t);
+	unsigned ndx = self->Index();
+	if (ndx >= level.sectors.Size())
+	{
+		// This qualifies as an array out of bounds exception. Normally it can only happen when a sector copy is concerned which scripts should not be able to create.
+		ThrowAbortException(X_ARRAY_OUT_OF_BOUNDS, "Accessed invalid sector");
+	}
+	ACTION_RETURN_INT(ndx);
+ }
+
+ //===========================================================================
+ //
+ //  line_t exports
+ //
+ //===========================================================================
+
+ DEFINE_ACTION_FUNCTION(_Line, isLinePortal)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(line_t);
+	 ACTION_RETURN_BOOL(self->isLinePortal());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Line, isVisualPortal)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(line_t);
+	 ACTION_RETURN_BOOL(self->isVisualPortal());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Line, getPortalDestination)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(line_t);
+	 ACTION_RETURN_POINTER(self->getPortalDestination());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Line, getPortalAlignment)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(line_t);
+	 ACTION_RETURN_INT(self->getPortalAlignment());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Line, Index)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(line_t);
+	 unsigned ndx = self->Index();
+	 if (ndx >= level.lines.Size())
+	 {
+		 ThrowAbortException(X_ARRAY_OUT_OF_BOUNDS, "Accessed invalid line");
+	 }
+	 ACTION_RETURN_INT(ndx);
+ }
+
+ //===========================================================================
+ //
+ // 
+ //
+ //===========================================================================
+
+ DEFINE_ACTION_FUNCTION(_Side, GetTexture)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 ACTION_RETURN_INT(self->GetTexture(which).GetIndex());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, SetTexture)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_INT(tex);
+	 self->SetTexture(which, FSetTextureID(tex));
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, SetTextureXOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->SetTextureXOffset(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, AddTextureXOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->AddTextureXOffset(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, GetTextureXOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 ACTION_RETURN_FLOAT(self->GetTextureXOffset(which));
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, SetTextureYOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->SetTextureYOffset(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, AddTextureYOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->AddTextureYOffset(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, GetTextureYOffset)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 ACTION_RETURN_FLOAT(self->GetTextureYOffset(which));
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, SetTextureXScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->SetTextureXScale(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, MultiplyTextureXScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->MultiplyTextureXScale(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, GetTextureXScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 ACTION_RETURN_FLOAT(self->GetTextureXScale(which));
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, SetTextureYScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->SetTextureYScale(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, MultiplyTextureYScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 PARAM_FLOAT(ofs);
+	 self->MultiplyTextureYScale(which, ofs);
+	 return 0;
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, GetTextureYScale)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 PARAM_INT(which);
+	 ACTION_RETURN_FLOAT(self->GetTextureYScale(which));
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, V1)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 ACTION_RETURN_POINTER(self->V1());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, V2)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 ACTION_RETURN_POINTER(self->V2());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Side, Index)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(side_t);
+	 ACTION_RETURN_INT(self->Index());
+ }
+
+ DEFINE_ACTION_FUNCTION(_Vertex, Index)
+ {
+	 PARAM_SELF_STRUCT_PROLOGUE(vertex_t);
+	 ACTION_RETURN_INT(self->Index());
+ }
+
 //===========================================================================
 //
 // 
@@ -1838,7 +2038,7 @@ bool secplane_t::CopyPlaneIfValid (secplane_t *dest, const secplane_t *opp) cons
 
 bool P_AlignFlat (int linenum, int side, int fc)
 {
-	line_t *line = lines + linenum;
+	line_t *line = &level.lines[linenum];
 	sector_t *sec = side ? line->backsector : line->frontsector;
 
 	if (!sec)
@@ -1871,10 +2071,10 @@ void subsector_t::BuildPolyBSP()
 	assert((BSP == NULL || BSP->bDirty) && "BSP computed more than once");
 
 	// Set up level information for the node builder.
-	PolyNodeLevel.Sides = sides;
-	PolyNodeLevel.NumSides = numsides;
-	PolyNodeLevel.Lines = lines;
-	PolyNodeLevel.NumLines = numlines;
+	PolyNodeLevel.Sides = &level.sides[0];
+	PolyNodeLevel.NumSides = level.sides.Size();
+	PolyNodeLevel.Lines = &level.lines[0];
+	PolyNodeLevel.NumLines = numlines; // is this correct???
 
 	// Feed segs to the nodebuilder and build the nodes.
 	PolyNodeBuilder.Clear();
@@ -2100,6 +2300,12 @@ DEFINE_FIELD_X(Line, line_t, backsector)
 DEFINE_FIELD_X(Line, line_t, validcount)
 DEFINE_FIELD_X(Line, line_t, locknumber)
 DEFINE_FIELD_X(Line, line_t, portalindex)
+DEFINE_FIELD_X(Line, line_t, portaltransferred)
+
+DEFINE_FIELD_X(Side, side_t, sector)
+DEFINE_FIELD_X(Side, side_t, linedef)
+DEFINE_FIELD_X(Side, side_t, Light)
+DEFINE_FIELD_X(Side, side_t, Flags)
 
 DEFINE_FIELD_X(Secplane, secplane_t, normal)
 DEFINE_FIELD_X(Secplane, secplane_t, D)
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index e03b7ac23..ad713fab9 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -73,6 +73,8 @@
 #include "p_blockmap.h"
 #include "r_utility.h"
 #include "p_spec.h"
+#include "p_saveg.h"
+#include "g_levellocals.h"
 #ifndef NO_EDATA
 #include "edata.h"
 #endif
@@ -88,7 +90,6 @@ void BloodCrypt (void *data, int key, int len);
 void P_ClearUDMFKeys();
 
 extern AActor *P_SpawnMapThing (FMapThing *mthing, int position);
-extern bool P_LoadBuildMap (BYTE *mapdata, size_t len, FMapThing **things, int *numthings);
 
 extern void P_TranslateTeleportThings (void);
 
@@ -106,25 +107,25 @@ CVAR (Bool, showloadtimes, false, 0);
 
 static void P_Shutdown ();
 
-bool P_IsBuildMap(MapData *map);
+inline bool P_IsBuildMap(MapData *map)
+{
+	return false;
+}
+
+inline bool P_LoadBuildMap(BYTE *mapdata, size_t len, FMapThing **things, int *numthings)
+{
+	return false;
+}
 
 
 //
 // MAP related Lookup tables.
 // Store VERTEXES, LINEDEFS, SIDEDEFS, etc.
 //
-int 			numvertexes;
-vertex_t*		vertexes;
-int 			numvertexdatas;
-vertexdata_t*		vertexdatas;
+TArray<vertexdata_t> vertexdatas;
 
 int 			numsegs;
 seg_t*			segs;
-glsegextra_t*	glsegextras;
-
-//int 			numsectors;
-//sector_t*		sectors;
-TArray<sector_t>	loadsectors;
 
 int 			numsubsectors;
 subsector_t*	subsectors;
@@ -132,14 +133,6 @@ subsector_t*	subsectors;
 int 			numnodes;
 node_t* 		nodes;
 
-int 			numlines;
-line_t* 		lines;
-TArray<line_t>	loadlines;
-
-int 			numsides;
-side_t* 		sides;
-TArray<side_t>	loadsides;
-
 TArray<zone_t>	Zones;
 
 node_t * 		gamenodes;
@@ -195,7 +188,7 @@ TArray<FPlayerStart> deathmatchstarts (16);
 FPlayerStart		playerstarts[MAXPLAYERS];
 TArray<FPlayerStart> AllPlayerStarts;
 
-static void P_AllocateSideDefs (int count);
+static void P_AllocateSideDefs (MapData *map, int count);
 
 
 //===========================================================================
@@ -594,11 +587,11 @@ static void SetTexture (side_t *side, int position, const char *name, FMissingTe
 		{
 			// Print an error that lists all references to this sidedef.
 			// We must scan the linedefs manually for all references to this sidedef.
-			for(int i = 0; i < numlines; i++)
+			for(unsigned i = 0; i < level.lines.Size(); i++)
 			{
 				for(int j = 0; j < 2; j++)
 				{
-					if (lines[i].sidedef[j] == side)
+					if (level.lines[i].sidedef[j] == side)
 					{
 						Printf(TEXTCOLOR_RED"Unknown %s texture '"
 							TEXTCOLOR_ORANGE "%s" TEXTCOLOR_RED
@@ -836,12 +829,9 @@ void P_FloodZones ()
 
 void P_LoadVertexes (MapData * map)
 {
-	int i;
-
 	// Determine number of vertices:
 	//	total lump length / vertex record length.
-	numvertexes = map->Size(ML_VERTEXES) / sizeof(mapvertex_t);
-	numvertexdatas = 0;
+	unsigned numvertexes = map->Size(ML_VERTEXES) / sizeof(mapvertex_t);
 
 	if (numvertexes == 0)
 	{
@@ -849,18 +839,18 @@ void P_LoadVertexes (MapData * map)
 	}
 
 	// Allocate memory for buffer.
-	vertexes = new vertex_t[numvertexes];		
-	vertexdatas = NULL;
+	level.vertexes.Alloc(numvertexes);
+	vertexdatas.Clear();
 
 	map->Seek(ML_VERTEXES);
 		
 	// Copy and convert vertex coordinates, internal representation as fixed.
-	for (i = 0; i < numvertexes; i++)
+	for (auto &v : level.vertexes)
 	{
-		SWORD x, y;
+		int16_t x, y;
 
 		(*map->file) >> x >> y;
-		vertexes[i].set(double(x), double(y));
+		v.set(double(x), double(y));
 	}
 }
 
@@ -881,9 +871,9 @@ void P_LoadZSegs (FileReaderBase &data)
 
 		data >> v1 >> v2 >> line >> side;
 
-		segs[i].v1 = &vertexes[v1];
-		segs[i].v2 = &vertexes[v2];
-		segs[i].linedef = ldef = &lines[line];
+		segs[i].v1 = &level.vertexes[v1];
+		segs[i].v2 = &level.vertexes[v2];
+		segs[i].linedef = ldef = &level.lines[line];
 		segs[i].sidedef = ldef->sidedef[side];
 		segs[i].frontsector = ldef->sidedef[side]->sector;
 		if (ldef->flags & ML_TWOSIDED && ldef->sidedef[side^1] != NULL)
@@ -931,7 +921,7 @@ void P_LoadGLZSegs (FileReaderBase &data, int type)
 			data >> side;
 
 			seg = subsectors[i].firstline + j;
-			seg->v1 = &vertexes[v1];
+			seg->v1 = &level.vertexes[v1];
 			if (j == 0)
 			{
 				seg[subsectors[i].numlines - 1].v2 = seg->v1;
@@ -940,12 +930,12 @@ void P_LoadGLZSegs (FileReaderBase &data, int type)
 			{
 				seg[-1].v2 = seg->v1;
 			}
-			glsegextras[seg - segs].PartnerSeg = partner;
+			seg->PartnerSeg = &segs[partner];
 			if (line != 0xFFFFFFFF)
 			{
 				line_t *ldef;
 
-				seg->linedef = ldef = &lines[line];
+				seg->linedef = ldef = &level.lines[line];
 				seg->sidedef = ldef->sidedef[side];
 				seg->frontsector = ldef->sidedef[side]->sector;
 				if (ldef->flags & ML_TWOSIDED && ldef->sidedef[side^1] != NULL)
@@ -978,23 +968,26 @@ void LoadZNodes(FileReaderBase &data, int glnodes)
 {
 	// Read extra vertices added during node building
 	DWORD orgVerts, newVerts;
-	vertex_t *newvertarray;
+	TStaticArray<vertex_t> newvertarray;
 	unsigned int i;
 
 	data >> orgVerts >> newVerts;
-	if (orgVerts > (DWORD)numvertexes)
+	if (orgVerts > level.vertexes.Size())
 	{ // These nodes are based on a map with more vertex data than we have.
 	  // We can't use them.
 		throw CRecoverableError("Incorrect number of vertexes in nodes.\n");
 	}
-	if (orgVerts + newVerts == (DWORD)numvertexes)
+	bool fix;
+	if (orgVerts + newVerts == level.vertexes.Size())
 	{
-		newvertarray = vertexes;
+		newvertarray = std::move(level.vertexes);
+		fix = false;
 	}
 	else
 	{
-		newvertarray = new vertex_t[orgVerts + newVerts];
-		memcpy (newvertarray, vertexes, orgVerts * sizeof(vertex_t));
+		newvertarray.Alloc(orgVerts + newVerts);
+		memcpy (&newvertarray[0], &level.vertexes[0], orgVerts * sizeof(vertex_t));
+		fix = true;
 	}
 	for (i = 0; i < newVerts; ++i)
 	{
@@ -1002,16 +995,14 @@ void LoadZNodes(FileReaderBase &data, int glnodes)
 		data >> x >> y;
 		newvertarray[i + orgVerts].set(x, y);
 	}
-	if (vertexes != newvertarray)
+	if (fix)
 	{
-		for (i = 0; i < (DWORD)numlines; ++i)
+		for (auto &line : level.lines)
 		{
-			lines[i].v1 = lines[i].v1 - vertexes + newvertarray;
-			lines[i].v2 = lines[i].v2 - vertexes + newvertarray;
+			line.v1 = line.v1 - &level.vertexes[0] + &newvertarray[0];
+			line.v2 = line.v2 - &level.vertexes[0] + &newvertarray[0];
 		}
-		delete[] vertexes;
-		vertexes = newvertarray;
-		numvertexes = orgVerts + newVerts;
+		level.vertexes = std::move(newvertarray);
 	}
 
 	// Read the subsectors
@@ -1047,7 +1038,6 @@ void LoadZNodes(FileReaderBase &data, int glnodes)
 	numsegs = numSegs;
 	segs = new seg_t[numsegs];
 	memset (segs, 0, numsegs*sizeof(seg_t));
-	glsegextras = NULL;
 
 	for (i = 0; i < numSubs; ++i)
 	{
@@ -1060,7 +1050,6 @@ void LoadZNodes(FileReaderBase &data, int glnodes)
 	}
 	else
 	{
-		glsegextras = new glsegextra_t[numsegs];
 		P_LoadGLZSegs (data, glnodes);
 	}
 
@@ -1215,9 +1204,9 @@ void P_LoadSegs (MapData * map)
 {
 	int  i;
 	BYTE *data;
+	int numvertexes = level.vertexes.Size();
 	BYTE *vertchanged = new BYTE[numvertexes];	// phares 10/4/98
 	DWORD segangle;
-	line_t* line;		// phares 10/4/98
 	//int ptp_angle;		// phares 10/4/98
 	//int delta_angle;	// phares 10/4/98
 	int vnum1,vnum2;	// phares 10/4/98
@@ -1252,10 +1241,9 @@ void P_LoadSegs (MapData * map)
 	// Mark those used by linedefs. A marked vertex is one that is not a
 	// candidate for movement further down.
 
-	line = lines;
-	for (i = 0; i < numlines ; i++, line++)
+	for (auto &line : level.lines)
 	{
-		vertchanged[line->v1 - vertexes] = vertchanged[line->v2 - vertexes] = 1;
+		vertchanged[line.v1->Index()] = vertchanged[line.v2->Index()] = 1;
 	}
 
 	try
@@ -1276,8 +1264,8 @@ void P_LoadSegs (MapData * map)
 				throw badseg(0, i, MAX(vnum1, vnum2));
 			}
 
-			li->v1 = &vertexes[vnum1];
-			li->v2 = &vertexes[vnum2];
+			li->v1 = &level.vertexes[vnum1];
+			li->v2 = &level.vertexes[vnum2];
 
 			segangle = (WORD)LittleShort(ml->angle);
 
@@ -1332,16 +1320,16 @@ void P_LoadSegs (MapData * map)
 			}
 
 			linedef = LittleShort(ml->linedef);
-			if ((unsigned)linedef >= (unsigned)numlines)
+			if ((unsigned)linedef >= level.lines.Size())
 			{
 				throw badseg(1, i, linedef);
 			}
-			ldef = &lines[linedef];
+			ldef = &level.lines[linedef];
 			li->linedef = ldef;
 			side = LittleShort(ml->side);
-			if ((unsigned)(ldef->sidedef[side] - sides) >= (unsigned)numsides)
+			if ((unsigned)(ldef->sidedef[side]->Index()) >= level.sides.Size())
 			{
-				throw badseg(2, i, int(ldef->sidedef[side] - sides));
+				throw badseg(2, i, ldef->sidedef[side]->Index());
 			}
 			li->sidedef = ldef->sidedef[side];
 			li->frontsector = ldef->sidedef[side]->sector;
@@ -1367,11 +1355,11 @@ void P_LoadSegs (MapData * map)
 			break;
 
 		case 1:
-			Printf ("Seg %d references a nonexistant linedef %d (max %d).\n", bad.badsegnum, bad.baddata, numlines);
+			Printf ("Seg %d references a nonexistant linedef %d (max %u).\n", bad.badsegnum, bad.baddata, level.lines.Size());
 			break;
 
 		case 2:
-			Printf ("The linedef for seg %d references a nonexistant sidedef %d (max %d).\n", bad.badsegnum, bad.baddata, numsides);
+			Printf ("The linedef for seg %d references a nonexistant sidedef %d (max %d).\n", bad.badsegnum, bad.baddata, level.sides.Size());
 			break;
 		}
 		Printf ("The BSP will be rebuilt.\n");
@@ -1981,7 +1969,7 @@ void P_SaveLineSpecial (line_t *ld)
 	if (ld->sidedef[0] == NULL)
 		return;
 
-	DWORD sidenum = DWORD(ld->sidedef[0]-sides);
+	DWORD sidenum = ld->sidedef[0]->Index();
 	// killough 4/4/98: support special sidedef interpretation below
 	// [RH] Save Static_Init only if it's interested in the textures
 	if	(ld->special != Static_Init || ld->args[1] == Init_Color)
@@ -2003,7 +1991,7 @@ void P_FinishLoadingLineDef(line_t *ld, int alpha)
 	ld->backsector  = ld->sidedef[1] != NULL ? ld->sidedef[1]->sector : NULL;
 	double dx = (ld->v2->fX() - ld->v1->fX());
 	double dy = (ld->v2->fY() - ld->v1->fY());
-	int linenum = int(ld-lines);
+	int linenum = ld->Index();
 
 	if (ld->frontsector == NULL)
 	{
@@ -2027,8 +2015,6 @@ void P_FinishLoadingLineDef(line_t *ld, int alpha)
 
 	switch (ld->special)
 	{						// killough 4/11/98: handle special types
-		int j;
-
 	case TranslucentLine:			// killough 4/11/98: translucent 2s textures
 		// [RH] Second arg controls how opaque it is.
 		if (alpha == SHRT_MIN)
@@ -2053,14 +2039,14 @@ void P_FinishLoadingLineDef(line_t *ld, int alpha)
 		}
 		else
 		{
-			for (j = 0; j < numlines; j++)
+			for (unsigned j = 0; j < level.lines.Size(); j++)
 			{
 				if (tagManager.LineHasID(j, ld->args[0]))
 				{
-					lines[j].alpha = dalpha;
+					level.lines[j].alpha = dalpha;
 					if (additive)
 					{
-						lines[j].flags |= ML_ADDTRANS;
+						level.lines[j].flags |= ML_ADDTRANS;
 					}
 				}
 			}
@@ -2072,9 +2058,9 @@ void P_FinishLoadingLineDef(line_t *ld, int alpha)
 // killough 4/4/98: delay using sidedefs until they are loaded
 void P_FinishLoadingLineDefs ()
 {
-	for (int i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		P_FinishLoadingLineDef(&lines[i], sidetemp[lines[i].sidedef[0]-sides].a.alpha);
+		P_FinishLoadingLineDef(&line, sidetemp[line.sidedef[0]->Index()].a.alpha);
 	}
 }
 
@@ -2084,10 +2070,10 @@ static void P_SetSideNum (side_t **sidenum_p, WORD sidenum)
 	{
 		*sidenum_p = NULL;
 	}
-	else if (sidecount < numsides)
+	else if (sidecount < (int)level.sides.Size())
 	{
 		sidetemp[sidecount].a.map = sidenum;
-		*sidenum_p = &sides[sidecount++];
+		*sidenum_p = &level.sides[sidecount++];
 	}
 	else
 	{
@@ -2103,10 +2089,10 @@ void P_LoadLineDefs (MapData * map)
 	char * mldf;
 	maplinedef_t *mld;
 		
-	numlines = lumplen / sizeof(maplinedef_t);
-	lines = new line_t[numlines];
+	int numlines = lumplen / sizeof(maplinedef_t);
+	level.lines.Alloc(numlines);
 	linemap.Resize(numlines);
-	memset (lines, 0, numlines*sizeof(line_t));
+	memset (&level.lines[0], 0, numlines*sizeof(line_t));
 
 	mldf = new char[lumplen];
 	map->Read(ML_LINEDEFS, mldf);
@@ -2118,17 +2104,16 @@ void P_LoadLineDefs (MapData * map)
 	for (skipped = sidecount = i = 0; i < numlines; )
 	{
 		mld = ((maplinedef_t*)mldf) + i;
-		int v1 = LittleShort(mld->v1);
-		int v2 = LittleShort(mld->v2);
+		unsigned v1 = LittleShort(mld->v1);
+		unsigned v2 = LittleShort(mld->v2);
 
-		if (v1 >= numvertexes || v2 >= numvertexes)
+		if (v1 >= level.vertexes.Size() || v2 >= level.vertexes.Size())
 		{
 			delete [] mldf;
-			I_Error ("Line %d has invalid vertices: %d and/or %d.\nThe map only contains %d vertices.", i+skipped, v1, v2, numvertexes);
+			I_Error ("Line %d has invalid vertices: %d and/or %d.\nThe map only contains %u vertices.", i+skipped, v1, v2, level.vertexes.Size());
 		}
 		else if (v1 == v2 ||
-			(vertexes[LittleShort(mld->v1)].fX() == vertexes[LittleShort(mld->v2)].fX() &&
-			 vertexes[LittleShort(mld->v1)].fY() == vertexes[LittleShort(mld->v2)].fY()))
+			(level.vertexes[v1].fX() == level.vertexes[v2].fX() && level.vertexes[v1].fY() == level.vertexes[v2].fY()))
 		{
 			Printf ("Removing 0-length line %d\n", i+skipped);
 			memmove (mld, mld+1, sizeof(*mld)*(numlines-i-1));
@@ -2153,14 +2138,15 @@ void P_LoadLineDefs (MapData * map)
 		}
 	}
 
-	P_AllocateSideDefs (sidecount);
+	P_AllocateSideDefs (map, sidecount);
 
 	mld = (maplinedef_t *)mldf;
-	ld = lines;
+	ld = &level.lines[0];
 	for (i = 0; i < numlines; i++, mld++, ld++)
 	{
 		ld->alpha = 1.;	// [RH] Opaque by default
 		ld->portalindex = UINT_MAX;
+		ld->portaltransferred = UINT_MAX;
 
 		// [RH] Translate old linedef special and flags to be
 		//		compatible with the new format.
@@ -2178,8 +2164,8 @@ void P_LoadLineDefs (MapData * map)
 		}
 #endif
 
-		ld->v1 = &vertexes[LittleShort(mld->v1)];
-		ld->v2 = &vertexes[LittleShort(mld->v2)];
+		ld->v1 = &level.vertexes[LittleShort(mld->v1)];
+		ld->v2 = &level.vertexes[LittleShort(mld->v2)];
 
 		P_SetSideNum (&ld->sidedef[0], LittleShort(mld->sidenum[0]));
 		P_SetSideNum (&ld->sidedef[1], LittleShort(mld->sidenum[1]));
@@ -2202,10 +2188,10 @@ void P_LoadLineDefs2 (MapData * map)
 	char * mldf;
 	maplinedef2_t *mld;
 		
-	numlines = lumplen / sizeof(maplinedef2_t);
-	lines = new line_t[numlines];
+	int numlines = lumplen / sizeof(maplinedef2_t);
+	level.lines.Alloc(numlines);
 	linemap.Resize(numlines);
-	memset (lines, 0, numlines*sizeof(line_t));
+	memset (&level.lines[0], 0, numlines*sizeof(line_t));
 
 	mldf = new char[lumplen];
 	map->Read(ML_LINEDEFS, mldf);
@@ -2216,8 +2202,8 @@ void P_LoadLineDefs2 (MapData * map)
 		mld = ((maplinedef2_t*)mldf) + i;
 
 		if (mld->v1 == mld->v2 ||
-			(vertexes[LittleShort(mld->v1)].fX() == vertexes[LittleShort(mld->v2)].fX() &&
-			 vertexes[LittleShort(mld->v1)].fY() == vertexes[LittleShort(mld->v2)].fY()))
+			(level.vertexes[LittleShort(mld->v1)].fX() == level.vertexes[LittleShort(mld->v2)].fX() &&
+			 level.vertexes[LittleShort(mld->v1)].fY() == level.vertexes[LittleShort(mld->v2)].fY()))
 		{
 			Printf ("Removing 0-length line %d\n", i+skipped);
 			memmove (mld, mld+1, sizeof(*mld)*(numlines-i-1));
@@ -2245,15 +2231,16 @@ void P_LoadLineDefs2 (MapData * map)
 		ForceNodeBuild = true;
 	}
 
-	P_AllocateSideDefs (sidecount);
+	P_AllocateSideDefs (map, sidecount);
 
 	mld = (maplinedef2_t *)mldf;
-	ld = lines;
+	ld = &level.lines[0];
 	for (i = 0; i < numlines; i++, mld++, ld++)
 	{
 		int j;
 
 		ld->portalindex = UINT_MAX;
+		ld->portaltransferred = UINT_MAX;
 
 		for (j = 0; j < 5; j++)
 			ld->args[j] = mld->args[j];
@@ -2261,8 +2248,8 @@ void P_LoadLineDefs2 (MapData * map)
 		ld->flags = LittleShort(mld->flags);
 		ld->special = mld->special;
 
-		ld->v1 = &vertexes[LittleShort(mld->v1)];
-		ld->v2 = &vertexes[LittleShort(mld->v2)];
+		ld->v1 = &level.vertexes[LittleShort(mld->v1)];
+		ld->v2 = &level.vertexes[LittleShort(mld->v2)];
 		ld->alpha = 1.;	// [RH] Opaque by default
 
 		P_SetSideNum (&ld->sidedef[0], LittleShort(mld->sidenum[0]));
@@ -2294,26 +2281,22 @@ void P_LoadLineDefs2 (MapData * map)
 //
 // P_LoadSideDefs
 //
-// killough 4/4/98: split into two functions
-void P_LoadSideDefs (MapData * map)
-{
-	numsides = map->Size(ML_SIDEDEFS) / sizeof(mapsidedef_t);
-}
 
-static void P_AllocateSideDefs (int count)
+static void P_AllocateSideDefs (MapData *map, int count)
 {
 	int i;
 
-	sides = new side_t[count];
-	memset (sides, 0, count*sizeof(side_t));
+	level.sides.Alloc(count);
+	memset(&level.sides[0], 0, count * sizeof(side_t));
 
-	sidetemp = new sidei_t[MAX(count,numvertexes)];
+	sidetemp = new sidei_t[MAX<int>(count, level.vertexes.Size())];
 	for (i = 0; i < count; i++)
 	{
 		sidetemp[i].a.special = sidetemp[i].a.tag = 0;
 		sidetemp[i].a.alpha = SHRT_MIN;
 		sidetemp[i].a.map = NO_SIDE;
 	}
+	auto numsides = map->Size(ML_SIDEDEFS) / sizeof(mapsidedef_t);
 	if (count < numsides)
 	{
 		Printf ("Map has %d unused sidedefs\n", numsides - count);
@@ -2334,9 +2317,10 @@ static void P_LoopSidedefs (bool firstloop)
 	{
 		delete[] sidetemp;
 	}
-	sidetemp = new sidei_t[MAX(numvertexes, numsides)];
+	int numsides = level.sides.Size();
+	sidetemp = new sidei_t[MAX<int>(level.vertexes.Size(), numsides)];
 
-	for (i = 0; i < numvertexes; ++i)
+	for (i = 0; i < (int)level.vertexes.Size(); ++i)
 	{
 		sidetemp[i].b.first = NO_SIDE;
 		sidetemp[i].b.next = NO_SIDE;
@@ -2350,17 +2334,17 @@ static void P_LoopSidedefs (bool firstloop)
 	{
 		// For each vertex, build a list of sidedefs that use that vertex
 		// as their left edge.
-		line_t *line = sides[i].linedef;
-		int lineside = (line->sidedef[0] != &sides[i]);
-		int vert = int((lineside ? line->v2 : line->v1) - vertexes);
+		line_t *line = level.sides[i].linedef;
+		int lineside = (line->sidedef[0] != &level.sides[i]);
+		int vert = lineside ? line->v2->Index() : line->v1->Index();
 		
 		sidetemp[i].b.lineside = lineside;
 		sidetemp[i].b.next = sidetemp[vert].b.first;
 		sidetemp[vert].b.first = i;
 
 		// Set each side so that it is the only member of its loop
-		sides[i].LeftSide = NO_SIDE;
-		sides[i].RightSide = NO_SIDE;
+		level.sides[i].LeftSide = NO_SIDE;
+		level.sides[i].RightSide = NO_SIDE;
 	}
 
 	// For each side, find the side that is to its right and set the
@@ -2369,7 +2353,7 @@ static void P_LoopSidedefs (bool firstloop)
 	for (i = 0; i < numsides; ++i)
 	{
 		DWORD right;
-		line_t *line = sides[i].linedef;
+		line_t *line = level.sides[i].linedef;
 
 		// If the side's line only exists in a single sector,
 		// then consider that line to be a self-contained loop
@@ -2381,21 +2365,21 @@ static void P_LoopSidedefs (bool firstloop)
 			if (NULL == rightside)
 			{
 				// There is no right side!
-				if (firstloop) Printf ("Line %d's right edge is unconnected\n", linemap[unsigned(line-lines)]);
+				if (firstloop) Printf ("Line %d's right edge is unconnected\n", linemap[line->Index()]);
 				continue;
 			}
 
-			right = DWORD(rightside - sides);
+			right = rightside->Index();
 		}
 		else
 		{
 			if (sidetemp[i].b.lineside)
 			{
-				right = int(line->v1 - vertexes);
+				right = line->v1->Index();
 			}
 			else
 			{
-				right = int(line->v2 - vertexes);
+				right = line->v2->Index();
 			}
 
 			right = sidetemp[right].b.first;
@@ -2403,7 +2387,7 @@ static void P_LoopSidedefs (bool firstloop)
 			if (right == NO_SIDE)
 			{ 
 				// There is no right side!
-				if (firstloop) Printf ("Line %d's right edge is unconnected\n", linemap[unsigned(line-lines)]);
+				if (firstloop) Printf ("Line %d's right edge is unconnected\n", linemap[line->Index()]);
 				continue;
 			}
 
@@ -2414,7 +2398,7 @@ static void P_LoopSidedefs (bool firstloop)
 				line_t *leftline, *rightline;
 				DAngle ang1, ang2, ang;
 
-				leftline = sides[i].linedef;
+				leftline = level.sides[i].linedef;
 				ang1 = leftline->Delta().Angle();
 				if (!sidetemp[i].b.lineside)
 				{
@@ -2423,9 +2407,9 @@ static void P_LoopSidedefs (bool firstloop)
 
 				while (right != NO_SIDE)
 				{
-					if (sides[right].LeftSide == NO_SIDE)
+					if (level.sides[right].LeftSide == NO_SIDE)
 					{
-						rightline = sides[right].linedef;
+						rightline = level.sides[right].linedef;
 						if (rightline->frontsector != rightline->backsector)
 						{
 							ang2 = rightline->Delta().Angle();
@@ -2450,8 +2434,8 @@ static void P_LoopSidedefs (bool firstloop)
 		}
 		assert((unsigned)i<(unsigned)numsides);
 		assert(right<(unsigned)numsides);
-		sides[i].RightSide = right;
-		sides[right].LeftSide = i;
+		level.sides[i].RightSide = right;
+		level.sides[right].LeftSide = i;
 	}
 
 	// We keep the sidedef init info around until after polyobjects are initialized,
@@ -2607,14 +2591,13 @@ void P_ProcessSideTextures(bool checktranmap, side_t *sd, sector_t *sec, intmaps
 
 void P_LoadSideDefs2 (MapData *map, FMissingTextureTracker &missingtex)
 {
-	int  i;
 	char * msdf = new char[map->Size(ML_SIDEDEFS)];
 	map->Read(ML_SIDEDEFS, msdf);
 
-	for (i = 0; i < numsides; i++)
+	for (unsigned i = 0; i < level.sides.Size(); i++)
 	{
 		mapsidedef_t *msd = ((mapsidedef_t*)msdf) + sidetemp[i].a.map;
-		side_t *sd = sides + i;
+		side_t *sd = &level.sides[i];
 		sector_t *sec;
 
 		// [RH] The Doom renderer ignored the patch y locations when
@@ -2631,7 +2614,7 @@ void P_LoadSideDefs2 (MapData *map, FMissingTextureTracker &missingtex)
 		sd->SetTextureYScale(1.);
 		sd->linedef = NULL;
 		sd->Flags = 0;
-		sd->Index = i;
+		sd->UDMFIndex = i;
 
 		// killough 4/4/98: allow sidedef texture names to be overloaded
 		// killough 4/11/98: refined to allow colormaps to work as wall
@@ -2773,22 +2756,21 @@ static void P_CreateBlockMap ()
 	int bmapwidth, bmapheight;
 	double dminx, dmaxx, dminy, dmaxy;
 	int minx, maxx, miny, maxy;
-	int i;
 	int line;
 
-	if (numvertexes <= 0)
+	if (level.vertexes.Size() == 0)
 		return;
 
 	// Find map extents for the blockmap
-	dminx = dmaxx = vertexes[0].fX();
-	dminy = dmaxy = vertexes[0].fY();
+	dminx = dmaxx = level.vertexes[0].fX();
+	dminy = dmaxy = level.vertexes[0].fY();
 
-	for (i = 1; i < numvertexes; ++i)
+	for (auto &vert : level.vertexes)
 	{
-			 if (vertexes[i].fX() < dminx) dminx = vertexes[i].fX();
-		else if (vertexes[i].fX() > dmaxx) dmaxx = vertexes[i].fX();
-			 if (vertexes[i].fY() < dminy) dminy = vertexes[i].fY();
-		else if (vertexes[i].fY() > dmaxy) dmaxy = vertexes[i].fY();
+			 if (vert.fX() < dminx) dminx = vert.fX();
+		else if (vert.fX() > dmaxx) dmaxx = vert.fX();
+			 if (vert.fY() < dminy) dminy = vert.fY();
+		else if (vert.fY() > dmaxy) dmaxy = vert.fY();
 	}
 
 	minx = int(dminx);
@@ -2808,12 +2790,12 @@ static void P_CreateBlockMap ()
 
 	BlockLists = new TArray<int>[bmapwidth * bmapheight];
 
-	for (line = 0; line < numlines; ++line)
+	for (line = 0; line < (int)level.lines.Size(); ++line)
 	{
-		int x1 = int(lines[line].v1->fX());
-		int y1 = int(lines[line].v1->fY());
-		int x2 = int(lines[line].v2->fX());
-		int y2 = int(lines[line].v2->fY());
+		int x1 = int(level.lines[line].v1->fX());
+		int y1 = int(level.lines[line].v1->fY());
+		int x2 = int(level.lines[line].v2->fX());
+		int y2 = int(level.lines[line].v2->fY());
 		int dx = x2 - x1;
 		int dy = y2 - y1;
 		int bx = (x1 - minx) >> BLOCKBITS;
@@ -2996,7 +2978,7 @@ static bool P_VerifyBlockMap(int count)
 			// scan the list for out-of-range linedef indicies in list
 			for(tmplist = list; *tmplist != -1; tmplist++)
 			{
-				if(*tmplist < 0 || *tmplist >= numlines)
+				if((unsigned)*tmplist >= level.lines.Size())
 				{
 					Printf(PRINT_HIGH, "P_VerifyBlockMap: index >= numlines\n");
 					return false;
@@ -3105,14 +3087,11 @@ static void P_GroupLines (bool buildmap)
 	{
 		subsectors[i].sector = subsectors[i].firstline->sidedef->sector;
 	}
-	if (glsegextras != NULL)
+	for (int i = 0; i < numsubsectors; i++)
 	{
-		for (int i = 0; i < numsubsectors; i++)
+		for (jj = 0; jj < subsectors[i].numlines; ++jj)
 		{
-			for (jj = 0; jj < subsectors[i].numlines; ++jj)
-			{
-				glsegextras[subsectors[i].firstline - segs + jj].Subsector = &subsectors[i];
-			}
+			subsectors[i].firstline[jj].Subsector = &subsectors[i];
 		}
 	}
 	times[0].Unclock();
@@ -3120,9 +3099,9 @@ static void P_GroupLines (bool buildmap)
 	// count number of lines in each sector
 	times[1].Clock();
 	total = 0;
-	for (int i = 0; i < numlines; i++)
+	for (unsigned i = 0; i < level.lines.Size(); i++)
 	{
-		auto li = &lines[i];
+		auto li = &level.lines[i];
 		if (li->frontsector == NULL)
 		{
 			if (!flaggedNoFronts)
@@ -3174,9 +3153,9 @@ static void P_GroupLines (bool buildmap)
 		}
 	}
 
-	for (int i = 0; i < numlines; i++)
+	for (unsigned i = 0; i < level.lines.Size(); i++)
 	{
-		auto li = &lines[i];
+		auto li = &level.lines[i];
 		if (li->frontsector != NULL)
 		{
 			li->frontsector->Lines[linesDoneInEachSector[li->frontsector->Index()]++] = li;
@@ -3393,11 +3372,11 @@ static void P_PrecacheLevel()
 		hitlist[level.sectors[i].GetTexture(sector_t::ceiling).GetIndex()] |= FTextureManager::HIT_Flat;
 	}
 
-	for (i = numsides - 1; i >= 0; i--)
+	for (i = level.sides.Size() - 1; i >= 0; i--)
 	{
-		hitlist[sides[i].GetTexture(side_t::top).GetIndex()] |= FTextureManager::HIT_Wall;
-		hitlist[sides[i].GetTexture(side_t::mid).GetIndex()] |= FTextureManager::HIT_Wall;
-		hitlist[sides[i].GetTexture(side_t::bottom).GetIndex()] |= FTextureManager::HIT_Wall;
+		hitlist[level.sides[i].GetTexture(side_t::top).GetIndex()] |= FTextureManager::HIT_Wall;
+		hitlist[level.sides[i].GetTexture(side_t::mid).GetIndex()] |= FTextureManager::HIT_Wall;
+		hitlist[level.sides[i].GetTexture(side_t::bottom).GetIndex()] |= FTextureManager::HIT_Wall;
 	}
 
 	// Sky texture is always present.
@@ -3431,6 +3410,7 @@ extern polyblock_t **PolyBlockMap;
 
 void P_FreeLevelData ()
 {
+	P_FreeMapDataBackup();
 	interpolator.ClearInterpolations();	// [RH] Nothing to interpolate on a fresh level.
 	Renderer->CleanLevelData();
 	FPolyObj::ClearAllSubsectorLinks(); // can't be done as part of the polyobj deletion process.
@@ -3443,28 +3423,20 @@ void P_FreeLevelData ()
 		wminfo.maxfrags = 0;
 		
 	FBehavior::StaticUnloadModules ();
-	if (vertexes != NULL)
-	{
-		delete[] vertexes;
-		vertexes = NULL;
-	}
-	numvertexes = 0;
 	if (segs != NULL)
 	{
 		delete[] segs;
 		segs = NULL;
 	}
 	numsegs = 0;
-	if (glsegextras != NULL)
-	{
-		delete[] glsegextras;
-		glsegextras = NULL;
-	}
 	if (level.sectors.Size() > 0)
 	{
 		delete[] level.sectors[0].e;
 	}
 	level.sectors.Clear();
+	level.lines.Clear();
+	level.sides.Clear();
+	level.vertexes.Clear();
 
 	if (gamenodes != NULL && gamenodes != nodes)
 	{
@@ -3493,18 +3465,6 @@ void P_FreeLevelData ()
 	numsubsectors = numgamesubsectors = 0;
 	nodes = gamenodes = NULL;
 	numnodes = numgamenodes = 0;
-	if (lines != NULL)
-	{
-		delete[] lines;
-		lines = NULL;
-	}
-	numlines = 0;
-	if (sides != NULL)
-	{
-		delete[] sides;
-		sides = NULL;
-	}
-	numsides = 0;
 
 	if (blockmaplump != NULL)
 	{
@@ -3761,7 +3721,6 @@ void P_SetupLevel (const char *lumpname, int position)
 			times[1].Unclock();
 
 			times[2].Clock();
-			P_LoadSideDefs (map);
 			times[2].Unclock();
 
 			times[3].Clock();
@@ -3925,9 +3884,9 @@ void P_SetupLevel (const char *lumpname, int position)
 		P_GetPolySpots (map, polyspots, anchors);
 		FNodeBuilder::FLevel leveldata =
 		{
-			vertexes, numvertexes,
-			sides, numsides,
-			lines, numlines,
+			&level.vertexes[0], (int)level.vertexes.Size(),
+			&level.sides[0], (int)level.sides.Size(),
+			&level.lines[0], (int)level.lines.Size(),
 			0, 0, 0, 0
 		};
 		leveldata.FindMapBounds ();
@@ -3935,11 +3894,10 @@ void P_SetupLevel (const char *lumpname, int position)
 		// In case a sync critical game mode is started, also build GL nodes to avoid problems
 		// if the different machines' am_textured setting differs.
 		FNodeBuilder builder (leveldata, polyspots, anchors, BuildGLNodes);
-		delete[] vertexes;
 		builder.Extract (nodes, numnodes,
-			segs, glsegextras, numsegs,
+			segs, numsegs,
 			subsectors, numsubsectors,
-			vertexes, numvertexes);
+			level.vertexes);
 		endTime = I_FPSTime ();
 		DPrintf (DMSG_NOTIFY, "BSP generation took %.3f sec (%d segs)\n", (endTime - startTime) * 0.001, numsegs);
 		oldvertextable = builder.GetOldVertexTable();
@@ -4193,18 +4151,7 @@ void P_SetupLevel (const char *lumpname, int position)
 	MapThingsUserDataIndex.Clear();
 	MapThingsUserData.Clear();
 
-	loadsectors.Resize(level.sectors.Size());
-	memcpy(&loadsectors[0], &level.sectors[0], loadsectors.Size() * sizeof(sector_t));
-	loadlines.Resize(numlines);
-	memcpy(&loadlines[0], lines, numlines * sizeof(line_t));
-	loadsides.Resize(numsides);
-	memcpy(&loadsides[0], sides, numsides * sizeof(side_t));
-
-	if (glsegextras != NULL)
-	{
-		delete[] glsegextras;
-		glsegextras = NULL;
-	}
+	P_BackupMapData();
 }
 
 
diff --git a/src/p_setup.h b/src/p_setup.h
index 38d61c1eb..3d8c021a7 100644
--- a/src/p_setup.h
+++ b/src/p_setup.h
@@ -150,7 +150,6 @@ struct sidei_t	// [RH] Only keep BOOM sidedef init stuff around for init
 };
 extern sidei_t *sidetemp;
 extern bool hasglnodes;
-extern struct glsegextra_t *glsegextras;
 
 struct FMissingCount
 {
diff --git a/src/p_sight.cpp b/src/p_sight.cpp
index eb62e505a..74b9fe165 100644
--- a/src/p_sight.cpp
+++ b/src/p_sight.cpp
@@ -29,6 +29,7 @@
 #include "r_state.h"
 
 #include "stats.h"
+#include "g_levellocals.h"
 
 static FRandom pr_botchecksight ("BotCheckSight");
 static FRandom pr_checksight ("CheckSight");
@@ -116,6 +117,7 @@ public:
 		sightend = t2->PosRelative(task->portalgroup);
 		sightstart.Z += t1->Height * 0.75;
 
+		portalgroup = task->portalgroup;
 		Startfrac = task->Frac;
 		Trace = { sightstart.X, sightstart.Y, sightend.X - sightstart.X, sightend.Y - sightstart.Y };
 		Lastztop = Lastzbottom = sightstart.Z;
@@ -482,7 +484,7 @@ int SightCheck::P_SightBlockLinesIterator (int x, int y)
 
 	for (list = blockmaplump + offset + 1; *list != -1; list++)
 	{
-		if (!P_SightCheckLine (&lines[*list]))
+		if (!P_SightCheckLine (&level.lines[*list]))
 		{
 			if (!portalfound) return 0;
 			else res = -1;
@@ -790,6 +792,7 @@ sightcounts[2]++;
 
 	bool traverseres = P_SightTraverseIntercepts ( );
 	if (itres == -1) return false;	// if the iterator had an early out there was no line of sight. The traverser was only called to collect more portals.
+	if (seeingthing->Sector->PortalGroup != portalgroup) return false;	// We are in a different group than the seeingthing, so this trace cannot determine visibility alone.
 	return traverseres;
 }
 
diff --git a/src/p_slopes.cpp b/src/p_slopes.cpp
index ff0159940..c574d189b 100644
--- a/src/p_slopes.cpp
+++ b/src/p_slopes.cpp
@@ -38,6 +38,7 @@
 #include "p_lnspec.h"
 #include "p_maputl.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 //===========================================================================
 //
@@ -52,7 +53,7 @@ static void P_SlopeLineToPoint (int lineid, const DVector3 &pos, bool slopeCeil)
 	FLineIdIterator itr(lineid);
 	while ((linenum = itr.Next()) >= 0)
 	{
-		const line_t *line = &lines[linenum];
+		const line_t *line = &level.lines[linenum];
 		sector_t *sec;
 		secplane_t *plane;
 		
@@ -257,9 +258,9 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 		{
 			if (mt->info->Special == SMT_VertexFloorZ || mt->info->Special == SMT_VertexCeilingZ)
 			{
-				for (int i = 0; i < numvertexes; i++)
+				for (unsigned i = 0; i < level.vertexes.Size(); i++)
 				{
-					if (vertexes[i].fX() == mt->pos.X && vertexes[i].fY() == mt->pos.Y)
+					if (level.vertexes[i].fX() == mt->pos.X && level.vertexes[i].fY() == mt->pos.Y)
 					{
 						if (mt->info->Special == SMT_VertexFloorZ)
 						{
@@ -277,7 +278,7 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 		}
 	}
 
-	for(int i = 0; i < numvertexdatas; i++)
+	for(unsigned i = 0; i < vertexdatas.Size(); i++)
 	{
 		int ii = oldvertextable == NULL ? i : oldvertextable[i];
 
@@ -295,9 +296,8 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 	}
 
 	// If vertexdata_t is ever extended for non-slope usage, this will obviously have to be deferred or removed.
-	delete[] vertexdatas;
-	vertexdatas = NULL;
-	numvertexdatas = 0;
+	vertexdatas.Clear();
+	vertexdatas.ShrinkToFit();
 
 	if (vt_found)
 	{
@@ -309,14 +309,14 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 			DVector3 vec1, vec2;
 			int vi1, vi2, vi3;
 
-			vi1 = int(sec.Lines[0]->v1 - vertexes);
-			vi2 = int(sec.Lines[0]->v2 - vertexes);
+			vi1 = sec.Lines[0]->v1->Index();
+			vi2 = sec.Lines[0]->v2->Index();
 			vi3 = (sec.Lines[1]->v1 == sec.Lines[0]->v1 || sec.Lines[1]->v1 == sec.Lines[0]->v2)?
-				int(sec.Lines[1]->v2 - vertexes) : int(sec.Lines[1]->v1 - vertexes);
+				sec.Lines[1]->v2->Index() : sec.Lines[1]->v1->Index();
 
-			vt1 = DVector3(vertexes[vi1].fPos(), 0);
-			vt2 = DVector3(vertexes[vi2].fPos(), 0);
-			vt3 = DVector3(vertexes[vi3].fPos(), 0);
+			vt1 = DVector3(level.vertexes[vi1].fPos(), 0);
+			vt2 = DVector3(level.vertexes[vi2].fPos(), 0);
+			vt3 = DVector3(level.vertexes[vi3].fPos(), 0);
 
 			for(int j=0; j<2; j++)
 			{
@@ -329,7 +329,7 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 				vt2.Z = h2? *h2 : j==0? sec.GetPlaneTexZ(sector_t::floor) : sec.GetPlaneTexZ(sector_t::ceiling);
 				vt3.Z = h3? *h3 : j==0? sec.GetPlaneTexZ(sector_t::floor) : sec.GetPlaneTexZ(sector_t::ceiling);
 
-				if (P_PointOnLineSidePrecise(vertexes[vi3].fX(), vertexes[vi3].fY(), sec.Lines[0]) == 0)
+				if (P_PointOnLineSidePrecise(level.vertexes[vi3].fX(), level.vertexes[vi3].fY(), sec.Lines[0]) == 0)
 				{
 					vec1 = vt2 - vt3;
 					vec2 = vt1 - vt3;
@@ -359,7 +359,7 @@ static void P_SetSlopesFromVertexHeights(FMapThing *firstmt, FMapThing *lastmt,
 
 				secplane_t *plane = j==0? &sec.floorplane : &sec.ceilingplane;
 
-				double dist = -cross[0] * vertexes[vi3].fX() - cross[1] * vertexes[vi3].fY() - cross[2] * vt3.Z;
+				double dist = -cross[0] * level.vertexes[vi3].fX() - cross[1] * level.vertexes[vi3].fY() - cross[2] * vt3.Z;
 				plane->set(cross[0], cross[1], cross[2], dist);
 			}
 		}
@@ -516,14 +516,14 @@ static void P_AlignPlane(sector_t *sec, line_t *line, int which)
 
 void P_SetSlopes ()
 {
-	int i, s;
+	int s;
 
-	for (i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		if (lines[i].special == Plane_Align)
+		if (line.special == Plane_Align)
 		{
-			lines[i].special = 0;
-			if (lines[i].backsector != NULL)
+			line.special = 0;
+			if (line.backsector != nullptr)
 			{
 				// args[0] is for floor, args[1] is for ceiling
 				//
@@ -531,15 +531,15 @@ void P_SetSlopes ()
 				// then args[0], bits 2-3 are for ceiling.
 				for (s = 0; s < 2; s++)
 				{
-					int bits = lines[i].args[s] & 3;
+					int bits = line.args[s] & 3;
 
 					if (s == 1 && bits == 0)
-						bits = (lines[i].args[0] >> 2) & 3;
+						bits = (line.args[0] >> 2) & 3;
 
 					if (bits == 1)			// align front side to back
-						P_AlignPlane (lines[i].frontsector, lines + i, s);
+						P_AlignPlane (line.frontsector, &line, s);
 					else if (bits == 2)		// align back side to front
-						P_AlignPlane (lines[i].backsector, lines + i, s);
+						P_AlignPlane (line.backsector, &line, s);
 				}
 			}
 		}
@@ -554,9 +554,9 @@ void P_SetSlopes ()
 
 void P_CopySlopes()
 {
-	for (int i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		if (lines[i].special == Plane_Copy)
+		if (line.special == Plane_Copy)
 		{
 			// The args are used for the tags of sectors to copy:
 			// args[0]: front floor
@@ -564,31 +564,31 @@ void P_CopySlopes()
 			// args[2]: back floor
 			// args[3]: back ceiling
 			// args[4]: copy slopes from one side of the line to the other.
-			lines[i].special = 0;
-			for (int s = 0; s < (lines[i].backsector ? 4 : 2); s++)
+			line.special = 0;
+			for (int s = 0; s < (line.backsector ? 4 : 2); s++)
 			{
-				if (lines[i].args[s])
-					P_CopyPlane(lines[i].args[s], 
-					(s & 2 ? lines[i].backsector : lines[i].frontsector), s & 1);
+				if (line.args[s])
+					P_CopyPlane(line.args[s], 
+					(s & 2 ? line.backsector : line.frontsector), s & 1);
 			}
 
-			if (lines[i].backsector != NULL)
+			if (line.backsector != NULL)
 			{
-				if ((lines[i].args[4] & 3) == 1)
+				if ((line.args[4] & 3) == 1)
 				{
-					lines[i].backsector->floorplane = lines[i].frontsector->floorplane;
+					line.backsector->floorplane = line.frontsector->floorplane;
 				}
-				else if ((lines[i].args[4] & 3) == 2)
+				else if ((line.args[4] & 3) == 2)
 				{
-					lines[i].frontsector->floorplane = lines[i].backsector->floorplane;
+					line.frontsector->floorplane = line.backsector->floorplane;
 				}
-				if ((lines[i].args[4] & 12) == 4)
+				if ((line.args[4] & 12) == 4)
 				{
-					lines[i].backsector->ceilingplane = lines[i].frontsector->ceilingplane;
+					line.backsector->ceilingplane = line.frontsector->ceilingplane;
 				}
-				else if ((lines[i].args[4] & 12) == 8)
+				else if ((line.args[4] & 12) == 8)
 				{
-					lines[i].frontsector->ceilingplane = lines[i].backsector->ceilingplane;
+					line.frontsector->ceilingplane = line.backsector->ceilingplane;
 				}
 			}
 		}
diff --git a/src/p_spec.cpp b/src/p_spec.cpp
index 45f4d043c..b3953b1bd 100644
--- a/src/p_spec.cpp
+++ b/src/p_spec.cpp
@@ -70,6 +70,7 @@
 #include "d_player.h"
 #include "p_maputl.h"
 #include "p_blockmap.h"
+#include "g_levellocals.h"
 #ifndef NO_EDATA
 #include "edata.h"
 #endif
@@ -189,7 +190,7 @@ bool P_ActivateLine (line_t *line, AActor *mo, int side, int activationType, DVe
 // end of changed code
 	if (developer >= DMSG_SPAMMY && buttonSuccess)
 	{
-		Printf ("Line special %d activated on line %i\n", special, int(line - lines));
+		Printf ("Line special %d activated on line %i\n", special, line->Index());
 	}
 	return true;
 }
@@ -361,7 +362,7 @@ bool P_PredictLine(line_t *line, AActor *mo, int side, int activationType)
 	// end of changed code
 	if (developer >= DMSG_SPAMMY && buttonSuccess)
 	{
-		Printf("Line special %d predicted on line %i\n", special, int(line - lines));
+		Printf("Line special %d predicted on line %i\n", special, line->Index());
 	}
 	return true;
 }
@@ -790,14 +791,14 @@ DWallLightTransfer::DWallLightTransfer (sector_t *srcSec, int target, BYTE flags
 	FLineIdIterator itr(target);
 	while ((linenum = itr.Next()) >= 0)
 	{
-		if (flags & WLF_SIDE1 && lines[linenum].sidedef[0] != NULL)
+		if (flags & WLF_SIDE1 && level.lines[linenum].sidedef[0] != NULL)
 		{
-			lines[linenum].sidedef[0]->Flags |= wallflags;
+			level.lines[linenum].sidedef[0]->Flags |= wallflags;
 		}
 
-		if (flags & WLF_SIDE2 && lines[linenum].sidedef[1] != NULL)
+		if (flags & WLF_SIDE2 && level.lines[linenum].sidedef[1] != NULL)
 		{
-			lines[linenum].sidedef[1]->Flags |= wallflags;
+			level.lines[linenum].sidedef[1]->Flags |= wallflags;
 		}
 	}
 	ChangeStatNum(STAT_LIGHTTRANSFER);
@@ -821,7 +822,7 @@ void DWallLightTransfer::DoTransfer (short lightlevel, int target, BYTE flags)
 	FLineIdIterator itr(target);
 	while ((linenum = itr.Next()) >= 0)
 	{
-		line_t *line = &lines[linenum];
+		line_t *line = &level.lines[linenum];
 
 		if (flags & WLF_SIDE1 && line->sidedef[0] != NULL)
 		{
@@ -958,42 +959,42 @@ static void CopyPortal(int sectortag, int plane, unsigned pnum, double alpha, bo
 		SetPortal(&level.sectors[s], plane, pnum, alpha);
 	}
 
-	for (int j=0;j<numlines;j++)
+	for (auto &line : level.lines)
 	{
 		// Check if this portal needs to be copied to other sectors
 		// This must be done here to ensure that it gets done only after the portal is set up
-		if (lines[j].special == Sector_SetPortal &&
-			lines[j].args[1] == 1 &&
-			(lines[j].args[2] == plane || lines[j].args[2] == 3) &&
-			lines[j].args[3] == sectortag)
+		if (line.special == Sector_SetPortal &&
+			line.args[1] == 1 &&
+			(line.args[2] == plane || line.args[2] == 3) &&
+			line.args[3] == sectortag)
 		{
-			if (lines[j].args[0] == 0)
+			if (line.args[0] == 0)
 			{
-				SetPortal(lines[j].frontsector, plane, pnum, alpha);
+				SetPortal(line.frontsector, plane, pnum, alpha);
 			}
 			else
 			{
-				FSectorTagIterator itr(lines[j].args[0]);
+				FSectorTagIterator itr(line.args[0]);
 				while ((s = itr.Next()) >= 0)
 				{
 					SetPortal(&level.sectors[s], plane, pnum, alpha);
 				}
 			}
 		}
-		if (tolines && lines[j].special == Sector_SetPortal &&
-			lines[j].args[1] == 5 &&
-			lines[j].args[3] == sectortag)
+		if (tolines && line.special == Sector_SetPortal &&
+			line.args[1] == 5 &&
+			line.args[3] == sectortag)
 		{
-			if (lines[j].args[0] == 0)
+			if (line.args[0] == 0)
 			{
-				lines[j].portaltransferred = pnum;
+				line.portaltransferred = pnum;
 			}
 			else
 			{
-				FLineIdIterator itr(lines[j].args[0]);
+				FLineIdIterator itr(line.args[0]);
 				while ((s = itr.Next()) >= 0)
 				{
-					lines[s].portaltransferred = pnum;
+					level.lines[s].portaltransferred = pnum;
 				}
 			}
 		}
@@ -1004,20 +1005,20 @@ static void CopyPortal(int sectortag, int plane, unsigned pnum, double alpha, bo
 void P_SpawnPortal(line_t *line, int sectortag, int plane, int bytealpha, int linked)
 {
 	if (plane < 0 || plane > 2 || (linked && plane == 2)) return;
-	for (int i=0;i<numlines;i++)
+	for (auto &oline : level.lines)
 	{
 		// We must look for the reference line with a linear search unless we want to waste the line ID for it
 		// which is not a good idea.
-		if (lines[i].special == Sector_SetPortal &&
-			lines[i].args[0] == sectortag &&
-			lines[i].args[1] == linked &&
-			lines[i].args[2] == plane &&
-			lines[i].args[3] == 1)
+		if (oline.special == Sector_SetPortal &&
+			oline.args[0] == sectortag &&
+			oline.args[1] == linked &&
+			oline.args[2] == plane &&
+			oline.args[3] == 1)
 		{
 			// beware of overflows.
 			DVector2 pos1 = line->v1->fPos() + line->Delta() / 2;
-			DVector2 pos2 = lines[i].v1->fPos() + lines[i].Delta() / 2;
-			unsigned pnum = P_GetPortal(linked ? PORTS_LINKEDPORTAL : PORTS_PORTAL, plane, line->frontsector, lines[i].frontsector, pos2 - pos1);
+			DVector2 pos2 = oline.v1->fPos() + oline.Delta() / 2;
+			unsigned pnum = P_GetPortal(linked ? PORTS_LINKEDPORTAL : PORTS_PORTAL, plane, line->frontsector, oline.frontsector, pos2 - pos1);
 			CopyPortal(sectortag, plane, pnum, bytealpha / 255., false);
 			return;
 		}
@@ -1266,9 +1267,9 @@ void P_SpawnSpecials (void)
 		P_SpawnSkybox(pt2);
 	}
 
-	for (int i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		switch (lines[i].special)
+		switch (line.special)
 		{
 			int s;
 			sector_t *sec;
@@ -1277,16 +1278,16 @@ void P_SpawnSpecials (void)
 		// support for drawn heights coming from different sector
 		case Transfer_Heights:
 			{
-				sec = lines[i].frontsector;
-				if (lines[i].args[1] & 2)
+				sec = line.frontsector;
+				if (line.args[1] & 2)
 				{
 					sec->MoreFlags |= SECF_FAKEFLOORONLY;
 				}
-				if (lines[i].args[1] & 4)
+				if (line.args[1] & 4)
 				{
 					sec->MoreFlags |= SECF_CLIPFAKEPLANES;
 				}
-				if (lines[i].args[1] & 8)
+				if (line.args[1] & 8)
 				{
 					sec->MoreFlags |= SECF_UNDERWATER;
 				}
@@ -1294,15 +1295,15 @@ void P_SpawnSpecials (void)
 				{
 					sec->MoreFlags |= SECF_FORCEDUNDERWATER;
 				}
-				if (lines[i].args[1] & 16)
+				if (line.args[1] & 16)
 				{
 					sec->MoreFlags |= SECF_IGNOREHEIGHTSEC;
 				}
-				if (lines[i].args[1] & 32)
+				if (line.args[1] & 32)
 				{
 					sec->MoreFlags |= SECF_NOFAKELIGHT;
 				}
-				FSectorTagIterator itr(lines[i].args[0]);
+				FSectorTagIterator itr(line.args[0]);
 				while ((s = itr.Next()) >= 0)
 				{
 					level.sectors[s].heightsec = sec;
@@ -1315,29 +1316,29 @@ void P_SpawnSpecials (void)
 		// killough 3/16/98: Add support for setting
 		// floor lighting independently (e.g. lava)
 		case Transfer_FloorLight:
-			new DLightTransfer (lines[i].frontsector, lines[i].args[0], true);
+			new DLightTransfer (line.frontsector, line.args[0], true);
 			break;
 
 		// killough 4/11/98: Add support for setting
 		// ceiling lighting independently
 		case Transfer_CeilingLight:
-			new DLightTransfer (lines[i].frontsector, lines[i].args[0], false);
+			new DLightTransfer (line.frontsector, line.args[0], false);
 			break;
 
 		// [Graf Zahl] Add support for setting lighting
 		// per wall independently
 		case Transfer_WallLight:
-			new DWallLightTransfer (lines[i].frontsector, lines[i].args[0], lines[i].args[1]);
+			new DWallLightTransfer (line.frontsector, line.args[0], line.args[1]);
 			break;
 
 		case Sector_Attach3dMidtex:
-			P_Attach3dMidtexLinesToSector(lines[i].frontsector, lines[i].args[0], lines[i].args[1], !!lines[i].args[2]);
+			P_Attach3dMidtexLinesToSector(line.frontsector, line.args[0], line.args[1], !!line.args[2]);
 			break;
 
 		case Sector_SetLink:
-			if (lines[i].args[0] == 0)
+			if (line.args[0] == 0)
 			{
-				P_AddSectorLinks(lines[i].frontsector, lines[i].args[1], lines[i].args[2], lines[i].args[3]);
+				P_AddSectorLinks(line.frontsector, line.args[1], line.args[2], line.args[3]);
 			}
 			break;
 
@@ -1355,30 +1356,29 @@ void P_SpawnSpecials (void)
 			// arg 2 = 0:floor, 1:ceiling, 2:both
 			// arg 3 = 0: anchor, 1: reference line
 			// arg 4 = for the anchor only: alpha
-			if ((lines[i].args[1] == 0 || lines[i].args[1] == 6) && lines[i].args[3] == 0)
+			if ((line.args[1] == 0 || line.args[1] == 6) && line.args[3] == 0)
 			{
-				P_SpawnPortal(&lines[i], lines[i].args[0], lines[i].args[2], lines[i].args[4], lines[i].args[1]);
+				P_SpawnPortal(&line, line.args[0], line.args[2], line.args[4], line.args[1]);
 			}
-			else if (lines[i].args[1] == 3 || lines[i].args[1] == 4)
+			else if (line.args[1] == 3 || line.args[1] == 4)
 			{
-				line_t *line = &lines[i];
-				unsigned pnum = P_GetPortal(line->args[1] == 3 ? PORTS_PLANE : PORTS_HORIZON, line->args[2], line->frontsector, NULL, { 0,0 });
-				CopyPortal(line->args[0], line->args[2], pnum, 0, true);
+				unsigned pnum = P_GetPortal(line.args[1] == 3 ? PORTS_PLANE : PORTS_HORIZON, line.args[2], line.frontsector, NULL, { 0,0 });
+				CopyPortal(line.args[0], line.args[2], pnum, 0, true);
 			}
 			break;
 
 		case Line_SetPortal:
-			P_SpawnLinePortal(&lines[i]);
+			P_SpawnLinePortal(&line);
 			break;
 
 		// [RH] ZDoom Static_Init settings
 		case Static_Init:
-			switch (lines[i].args[1])
+			switch (line.args[1])
 			{
 			case Init_Gravity:
 				{
-					double grav = lines[i].Delta().Length() / 100.;
-					FSectorTagIterator itr(lines[i].args[0]);
+					double grav = line.Delta().Length() / 100.;
+					FSectorTagIterator itr(line.args[0]);
 					while ((s = itr.Next()) >= 0)
 						level.sectors[s].gravity = grav;
 				}
@@ -1389,8 +1389,8 @@ void P_SpawnSpecials (void)
 
 			case Init_Damage:
 				{
-					int damage = int(lines[i].Delta().Length());
-					FSectorTagIterator itr(lines[i].args[0]);
+					int damage = int(line.Delta().Length());
+					FSectorTagIterator itr(line.args[0]);
 					while ((s = itr.Next()) >= 0)
 					{
 						sector_t *sec = &level.sectors[s];
@@ -1416,8 +1416,8 @@ void P_SpawnSpecials (void)
 				break;
 
 			case Init_SectorLink:
-				if (lines[i].args[3] == 0)
-					P_AddSectorLinksByID(lines[i].frontsector, lines[i].args[0], lines[i].args[2]);
+				if (line.args[3] == 0)
+					P_AddSectorLinksByID(line.frontsector, line.args[0], line.args[2]);
 				break;
 
 			// killough 10/98:
@@ -1431,9 +1431,9 @@ void P_SpawnSpecials (void)
 
 			case Init_TransferSky:
 				{
-					FSectorTagIterator itr(lines[i].args[0]);
+					FSectorTagIterator itr(line.args[0]);
 					while ((s = itr.Next()) >= 0)
-						level.sectors[s].sky = (i + 1) | PL_SKYFLAT;
+						level.sectors[s].sky = (line.Index() + 1) | PL_SKYFLAT;
 					break;
 				}
 			}
@@ -1499,10 +1499,9 @@ void P_SpawnSpecials (void)
 
 static void P_SpawnFriction(void)
 {
-	int i;
-	line_t *l = lines;
+	line_t *l = &level.lines[0];
 
-	for (i = 0 ; i < numlines ; i++,l++)
+	for (unsigned i = 0 ; i < level.lines.Size() ; i++,l++)
 	{
 		if (l->special == Sector_SetFriction)
 		{
diff --git a/src/p_tags.cpp b/src/p_tags.cpp
index dc71e2663..9e7d60d60 100644
--- a/src/p_tags.cpp
+++ b/src/p_tags.cpp
@@ -36,6 +36,7 @@
 
 #include "p_tags.h"
 #include "c_dispatch.h"
+#include "g_levellocals.h"
 
 FTagManager tagManager;
 
@@ -45,17 +46,6 @@ FTagManager tagManager;
 //
 //-----------------------------------------------------------------------------
 
-static inline int lineindex(const line_t *line)
-{
-	return (int)(intptr_t)(line - lines);
-}
-
-//-----------------------------------------------------------------------------
-//
-//
-//
-//-----------------------------------------------------------------------------
-
 void FTagManager::AddSectorTag(int sector, int tag)
 {
 	if (tag == 0) return;
@@ -244,7 +234,7 @@ bool FTagManager::SectorHasTag(const sector_t *sector, int tag) const
 
 int FTagManager::GetFirstLineID(const line_t *line) const
 {
-	int i = lineindex(line);
+	int i = line->Index();
 	return LineHasIDs(i) ? allIDs[startForLine[i]].tag : 0;
 }
 
@@ -276,7 +266,7 @@ bool FTagManager::LineHasID(int i, int tag) const
 
 bool FTagManager::LineHasID(const line_t *line, int tag) const
 {
-	return LineHasID(lineindex(line), tag);
+	return LineHasID(line->Index(), tag);
 }
 
 //-----------------------------------------------------------------------------
diff --git a/src/p_teleport.cpp b/src/p_teleport.cpp
index 12f9ef4b8..5eb63e4ce 100644
--- a/src/p_teleport.cpp
+++ b/src/p_teleport.cpp
@@ -38,6 +38,7 @@
 #include "p_maputl.h"
 #include "r_utility.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 #define FUDGEFACTOR		10
 
@@ -447,10 +448,10 @@ bool EV_SilentLineTeleport (line_t *line, int side, AActor *thing, int id, INTBO
 	FLineIdIterator itr(id);
 	while ((i = itr.Next()) >= 0)
 	{
-		if (line-lines == i)
+		if (line->Index() == i)
 			continue;
 
-		if ((l=lines+i) != line && l->backsector)
+		if ((l=&level.lines[i]) != line && l->backsector)
 		{
 			// Get the thing's position along the source linedef
 			double pos;
diff --git a/src/p_things.cpp b/src/p_things.cpp
index 6aac786f0..f6c06a1e5 100644
--- a/src/p_things.cpp
+++ b/src/p_things.cpp
@@ -51,6 +51,7 @@
 #include "p_spec.h"
 #include "math/cmath.h"
 #include "actorptrselect.h"
+#include "g_levellocals.h"
 
 // Set of spawnable things for the Thing_Spawn and Thing_Projectile specials.
 FClassMap SpawnableThings;
diff --git a/src/p_tick.cpp b/src/p_tick.cpp
index 332b7af81..2f8151425 100644
--- a/src/p_tick.cpp
+++ b/src/p_tick.cpp
@@ -35,6 +35,7 @@
 #include "g_level.h"
 #include "r_utility.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 extern gamestate_t wipegamestate;
 
diff --git a/src/p_trace.cpp b/src/p_trace.cpp
index 4b0a5f3bd..3597535e5 100644
--- a/src/p_trace.cpp
+++ b/src/p_trace.cpp
@@ -40,6 +40,7 @@
 #include "p_maputl.h"
 #include "r_defs.h"
 #include "p_spec.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/p_udmf.cpp b/src/p_udmf.cpp
index 63621d2fa..b0c9dbc15 100644
--- a/src/p_udmf.cpp
+++ b/src/p_udmf.cpp
@@ -48,6 +48,7 @@
 #include "w_wad.h"
 #include "p_tags.h"
 #include "p_terrain.h"
+#include "g_levellocals.h"
 
 //===========================================================================
 //
@@ -393,7 +394,6 @@ class UDMFParser : public UDMFParserBase
 	TArray<intmapsidedef_t> ParsedSideTextures;
 	TArray<sector_t> ParsedSectors;
 	TArray<vertex_t> ParsedVertices;
-	TArray<vertexdata_t> ParsedVertexDatas;
 
 	FDynamicColormap	*fogMap, *normMap;
 	FMissingTextureTracker &missingTex;
@@ -792,6 +792,7 @@ public:
 		memset(ld, 0, sizeof(*ld));
 		ld->alpha = 1.;
 		ld->portalindex = UINT_MAX;
+		ld->portaltransferred = UINT_MAX;
 		ld->sidedef[0] = ld->sidedef[1] = NULL;
 		if (level.flags2 & LEVEL2_CLIPMIDTEX) ld->flags |= ML_CLIP_MIDTEX;
 		if (level.flags2 & LEVEL2_WRAPMIDTEX) ld->flags |= ML_WRAP_MIDTEX;
@@ -1135,7 +1136,7 @@ public:
 		sdt->midtexture = "-";
 		sd->SetTextureXScale(1.);
 		sd->SetTextureYScale(1.);
-		sd->Index = index;
+		sd->UDMFIndex = index;
 
 		sc.MustGetToken('{');
 		while (!sc.CheckToken('}'))
@@ -1788,12 +1789,12 @@ public:
 			intptr_t v1i = intptr_t(ParsedLines[i].v1);
 			intptr_t v2i = intptr_t(ParsedLines[i].v2);
 
-			if (v1i >= numvertexes || v2i >= numvertexes || v1i < 0 || v2i < 0)
+			if (v1i >= level.vertexes.Size() || v2i >= level.vertexes.Size() || v1i < 0 || v2i < 0)
 			{
-				I_Error ("Line %d has invalid vertices: %zd and/or %zd.\nThe map only contains %d vertices.", i+skipped, v1i, v2i, numvertexes);
+				I_Error ("Line %d has invalid vertices: %zd and/or %zd.\nThe map only contains %u vertices.", i+skipped, v1i, v2i, level.vertexes.Size());
 			}
 			else if (v1i == v2i ||
-				(vertexes[v1i].fX() == vertexes[v2i].fX() && vertexes[v1i].fY() == vertexes[v2i].fY()))
+				(level.vertexes[v1i].fX() == level.vertexes[v2i].fX() && level.vertexes[v1i].fY() == level.vertexes[v2i].fY()))
 			{
 				Printf ("Removing 0-length line %d\n", i+skipped);
 				ParsedLines.Delete(i);
@@ -1802,8 +1803,8 @@ public:
 			}
 			else
 			{
-				ParsedLines[i].v1 = &vertexes[v1i];
-				ParsedLines[i].v2 = &vertexes[v2i];
+				ParsedLines[i].v1 = &level.vertexes[v1i];
+				ParsedLines[i].v2 = &level.vertexes[v2i];
 
 				if (ParsedLines[i].sidedef[0] != NULL)
 					sidecount++;
@@ -1813,13 +1814,14 @@ public:
 				i++;
 			}
 		}
-		numlines = ParsedLines.Size();
-		numsides = sidecount;
-		lines = new line_t[numlines];
-		sides = new side_t[numsides];
+		unsigned numlines = ParsedLines.Size();
+		level.sides.Alloc(sidecount);
+		level.lines.Alloc(numlines);
 		int line, side;
+		auto lines = &level.lines[0];
+		auto sides = &level.sides[0];
 
-		for(line = 0, side = 0; line < numlines; line++)
+		for(line = 0, side = 0; line < (int)numlines; line++)
 		{
 			short tempalpha[2] = { SHRT_MIN, SHRT_MIN };
 
@@ -1852,11 +1854,10 @@ public:
 			P_AdjustLine(&lines[line]);
 			P_FinishLoadingLineDef(&lines[line], tempalpha[0]);
 		}
-		assert(side <= numsides);
-		if (side < numsides)
+		assert((unsigned)side <= level.sides.Size());
+		if ((unsigned)side > level.sides.Size())
 		{
-			Printf("Map had %d invalid side references\n", numsides - side);
-			numsides = side;
+			Printf("Map had %d invalid side references\n", (int)level.sides.Size() - side);
 		}
 	}
 
@@ -1994,7 +1995,7 @@ public:
 				vertexdata_t vd;
 				ParseVertex(&vt, &vd);
 				ParsedVertices.Push(vt);
-				ParsedVertexDatas.Push(vd);
+				vertexdatas.Push(vd);
 			}
 			else
 			{
@@ -2009,14 +2010,8 @@ public:
 		if (ParsedSides.Size() == 0)	I_Error("Map has no sidedefs.\n");
 
 		// Create the real vertices
-		numvertexes = ParsedVertices.Size();
-		vertexes = new vertex_t[numvertexes];
-		memcpy(vertexes, &ParsedVertices[0], numvertexes * sizeof(*vertexes));
-
-		// Create the real vertex datas
-		numvertexdatas = ParsedVertexDatas.Size();
-		vertexdatas = new vertexdata_t[numvertexdatas];
-		memcpy(vertexdatas, &ParsedVertexDatas[0], numvertexdatas * sizeof(*vertexdatas));
+		level.vertexes.Alloc(ParsedVertices.Size());
+		memcpy(&level.vertexes[0], &ParsedVertices[0], level.vertexes.Size() * sizeof(vertex_t));
 
 		// Create the real sectors
 		level.sectors.Alloc(ParsedSectors.Size());
diff --git a/src/p_user.cpp b/src/p_user.cpp
index c4be5d526..936fdf4ad 100644
--- a/src/p_user.cpp
+++ b/src/p_user.cpp
@@ -61,6 +61,7 @@
 #include "virtual.h"
 #include "a_armor.h"
 #include "a_ammo.h"
+#include "g_levellocals.h"
 
 static FRandom pr_skullpop ("SkullPop");
 
diff --git a/src/p_writemap.cpp b/src/p_writemap.cpp
deleted file mode 100644
index cdf5a19d1..000000000
--- a/src/p_writemap.cpp
+++ /dev/null
@@ -1,226 +0,0 @@
-#include "p_local.h"
-#include "c_dispatch.h"
-#include "gi.h"
-#include "w_wad.h"
-#include "r_defs.h"
-#include "m_swap.h"
-#include "doomstat.h"
-#include "d_player.h"
-#include "p_spec.h"
-
-static int WriteTHINGS (FILE *file);
-static int WriteLINEDEFS (FILE *file);
-static int WriteSIDEDEFS (FILE *file);
-static int WriteVERTEXES (FILE *file);
-static int WriteSEGS (FILE *file);
-static int WriteSSECTORS (FILE *file);
-static int WriteNODES (FILE *file);
-static int WriteSECTORS (FILE *file);
-static int WriteREJECT (FILE *file);
-static int WriteBLOCKMAP (FILE *file);
-static int WriteBEHAVIOR (FILE *file);
-
-#define APPEND(pos,name) \
-	lumps[pos].FilePos = LittleLong((int)ftell (file)); \
-	lumps[pos].Size = LittleLong(Write##name (file)); \
-	memcpy (lumps[pos].Name, #name, sizeof(#name)-1);
-
-CCMD (dumpmap)
-{
-	const char *mapname;
-	FILE *file;
-
-	if (argv.argc() < 2)
-	{
-		Printf ("Usage: dumpmap <wadname> [mapname]\n");
-		return;
-	}
-	
-	if (gamestate != GS_LEVEL)
-	{
-		Printf ("You can only dump a map when inside a level.\n");
-		return;
-	}
-
-	if (argv.argc() < 3)
-	{
-		if (gameinfo.flags & GI_MAPxx)
-		{
-			mapname = "MAP01";
-		}
-		else
-		{
-			mapname = "E1M1";
-		}
-	}
-	else
-	{
-		mapname = argv[2];
-	}
-
-	file = fopen (argv[1], "wb");
-	if (file == NULL)
-	{
-		Printf ("Cannot write %s\n", argv[1]);
-		return;
-	}
-
-	wadinfo_t header = { PWAD_ID, 12, 0 };
-	wadlump_t lumps[12] = { {0, 0, {0}} };
-
-	fseek (file, 12, SEEK_SET);
-	
-	lumps[0].FilePos = LittleLong(12);
-	lumps[0].Size = 0;
-	uppercopy (lumps[0].Name, mapname);
-
-	APPEND(1, THINGS);
-	APPEND(2, LINEDEFS);
-	APPEND(3, SIDEDEFS);
-	APPEND(4, VERTEXES);
-	APPEND(5, SEGS);
-	APPEND(6, SSECTORS);
-	APPEND(7, NODES);
-	APPEND(8, SECTORS);
-	APPEND(9, REJECT);
-	APPEND(10, BLOCKMAP);
-	APPEND(11, BEHAVIOR);
-
-	header.InfoTableOfs = ftell (file);
-
-	fwrite (lumps, 16, 12, file);
-	fseek (file, 0, SEEK_SET);
-	fwrite (&header, 12, 1, file);
-
-	fclose (file);
-}
-
-static int WriteTHINGS (FILE *file)
-{
-	mapthinghexen_t mt = { 0, 0, 0, 0, 0, 0, 0, 0, {0} };
-	AActor *mo = players[consoleplayer].mo;
-
-	mt.x = LittleShort(short(mo->X()));
-	mt.y = LittleShort(short(mo->Y()));
-	mt.angle = LittleShort(short(mo->Angles.Yaw.Degrees));
-	mt.type = LittleShort((short)1);
-	mt.flags = LittleShort((short)(7|224|MTF_SINGLE));
-	fwrite (&mt, sizeof(mt), 1, file);
-	return sizeof (mt);
-}
-
-static int WriteLINEDEFS (FILE *file)
-{
-	maplinedef2_t mld;
-
-	for (int i = 0; i < numlines; ++i)
-	{
-		mld.v1 = LittleShort(short(lines[i].v1 - vertexes));
-		mld.v2 = LittleShort(short(lines[i].v2 - vertexes));
-		mld.flags = LittleShort(short(lines[i].flags));
-		mld.special = lines[i].special;
-		for (int j = 0; j < 5; ++j)
-		{
-			mld.args[j] = (BYTE)lines[i].args[j];
-		}
-		mld.sidenum[0] = LittleShort(WORD(lines[i].sidedef[0] - sides));
-		mld.sidenum[1] = LittleShort(WORD(lines[i].sidedef[1] - sides));
-		fwrite (&mld, sizeof(mld), 1, file);
-	}
-	return numlines * sizeof(mld);
-}
-
-static const char *GetTextureName (FTextureID texnum)
-{
-	FTexture *tex = TexMan[texnum];
-
-	if (tex != NULL)
-	{
-		return tex->Name;
-	}
-	else
-	{
-		return "-";
-	}
-}
-
-static int WriteSIDEDEFS (FILE *file)
-{
-	mapsidedef_t msd;
-
-	for (int i = 0; i < numsides; ++i)
-	{
-		msd.textureoffset = LittleShort(short(sides[i].GetTextureXOffset(side_t::mid)));
-		msd.rowoffset = LittleShort(short(sides[i].GetTextureYOffset(side_t::mid)));
-		msd.sector = LittleShort(short(sides[i].sector - &level.sectors[0]));
-		uppercopy (msd.toptexture, GetTextureName (sides[i].GetTexture(side_t::top)));
-		uppercopy (msd.bottomtexture, GetTextureName (sides[i].GetTexture(side_t::bottom)));
-		uppercopy (msd.midtexture, GetTextureName (sides[i].GetTexture(side_t::mid)));
-		fwrite (&msd, sizeof(msd), 1, file);
-	}
-	return numsides * sizeof(msd);
-}
-
-static int WriteVERTEXES (FILE *file)
-{
-	mapvertex_t mv;
-
-	for (int i = 0; i < numvertexes; ++i)
-	{
-		mv.x = LittleShort(short(vertexes[i].fixX() >> FRACBITS));
-		mv.y = LittleShort(short(vertexes[i].fixY() >> FRACBITS));
-		fwrite (&mv, sizeof(mv), 1, file);
-	}
-	return numvertexes * sizeof(mv);
-}
-
-
-static int WriteSEGS (FILE *file)
-{
-	return 0;
-}
-
-static int WriteSSECTORS (FILE *file)
-{
-	return 0;
-}
-
-static int WriteNODES (FILE *file)
-{
-	return 0;
-}
-
-static int WriteSECTORS (FILE *file)
-{
-	mapsector_t ms;
-
-	for (unsigned i = 0; i < level.sectors.Size(); ++i)
-	{
-		ms.floorheight = LittleShort(short(level.sectors[i].GetPlaneTexZ(sector_t::floor)));
-		ms.ceilingheight = LittleShort(short(level.sectors[i].GetPlaneTexZ(sector_t::ceiling)));
-		uppercopy (ms.floorpic, GetTextureName (level.sectors[i].GetTexture(sector_t::floor)));
-		uppercopy (ms.ceilingpic, GetTextureName (level.sectors[i].GetTexture(sector_t::ceiling)));
-		ms.lightlevel = LittleShort((short)level.sectors[i].lightlevel);
-		ms.special = LittleShort(level.sectors[i].special);
-		ms.tag = LittleShort(tagManager.GetFirstSectorTag(&level.sectors[i]));
-		fwrite (&ms, sizeof(ms), 1, file);
-	}
-	return level.sectors.Size() * sizeof(ms);
-}
-
-static int WriteREJECT (FILE *file)
-{
-	return 0;
-}
-
-static int WriteBLOCKMAP (FILE *file)
-{
-	return 0;
-}
-
-static int WriteBEHAVIOR (FILE *file)
-{
-	static const BYTE dummy[16] = { 'A', 'C', 'S', 0, 8 };
-	fwrite (dummy, 16, 1, file);
-	return 16;
-}
diff --git a/src/p_xlat.cpp b/src/p_xlat.cpp
index 424b93a52..29ccf966f 100644
--- a/src/p_xlat.cpp
+++ b/src/p_xlat.cpp
@@ -44,6 +44,7 @@
 #include "w_wad.h"
 #include "sc_man.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 #include "xlat/xlat.h"
 
 // define names for the TriggerType field of the general linedefs
@@ -317,27 +318,27 @@ void P_TranslateTeleportThings ()
 
 	if (foundSomething)
 	{
-		for (int i = 0; i < numlines; ++i)
+		for (auto &line : level.lines)
 		{
-			if (lines[i].special == Teleport)
+			if (line.special == Teleport)
 			{
-				if (lines[i].args[1] == 0)
+				if (line.args[1] == 0)
 				{
-					lines[i].args[0] = 1;
+					line.args[0] = 1;
 				}
 			}
-			else if (lines[i].special == Teleport_NoFog)
+			else if (line.special == Teleport_NoFog)
 			{
-				if (lines[i].args[2] == 0)
+				if (line.args[2] == 0)
 				{
-					lines[i].args[0] = 1;
+					line.args[0] = 1;
 				}
 			}
-			else if (lines[i].special == Teleport_ZombieChanger)
+			else if (line.special == Teleport_ZombieChanger)
 			{
-				if (lines[i].args[1] == 0)
+				if (line.args[1] == 0)
 				{
-					lines[i].args[0] = 1;
+					line.args[0] = 1;
 				}
 			}
 		}
diff --git a/src/po_man.cpp b/src/po_man.cpp
index 15c8d5a52..e8c1cbbb8 100644
--- a/src/po_man.cpp
+++ b/src/po_man.cpp
@@ -32,6 +32,7 @@
 #include "p_maputl.h"
 #include "r_utility.h"
 #include "p_blockmap.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -39,17 +40,6 @@
 
 // TYPES -------------------------------------------------------------------
 
-inline vertex_t *side_t::V1() const
-{
-	return this == linedef->sidedef[0]? linedef->v1 : linedef->v2;
-}
-
-inline vertex_t *side_t::V2() const
-{
-	return this == linedef->sidedef[0]? linedef->v2 : linedef->v1;
-}
-
-
 class DRotatePoly : public DPolyAction
 {
 	DECLARE_CLASS (DRotatePoly, DPolyAction)
@@ -148,8 +138,6 @@ static void ReleaseAllPolyNodes();
 
 // EXTERNAL DATA DECLARATIONS ----------------------------------------------
 
-extern seg_t *segs;
-
 // PUBLIC DATA DEFINITIONS -------------------------------------------------
 
 polyblock_t **PolyBlockMap;
@@ -1429,11 +1417,11 @@ static void InitBlockMap (void)
 
 static void InitSideLists ()
 {
-	for (int i = 0; i < numsides; ++i)
+	for (unsigned i = 0; i < level.sides.Size(); ++i)
 	{
-		if (sides[i].linedef != NULL &&
-			(sides[i].linedef->special == Polyobj_StartLine ||
-			 sides[i].linedef->special == Polyobj_ExplicitLine))
+		if (level.sides[i].linedef != NULL &&
+			(level.sides[i].linedef->special == Polyobj_StartLine ||
+				level.sides[i].linedef->special == Polyobj_ExplicitLine))
 		{
 			KnownPolySides.Push (i);
 		}
@@ -1491,7 +1479,7 @@ static void IterFindPolySides (FPolyObj *po, side_t *side)
 	assert(sidetemp != NULL);
 
 	vnum.Clear();
-	vnum.Push(DWORD(side->V1() - vertexes));
+	vnum.Push(DWORD(side->V1()->Index()));
 	vnumat = 0;
 
 	while (vnum.Size() != vnumat)
@@ -1499,8 +1487,8 @@ static void IterFindPolySides (FPolyObj *po, side_t *side)
 		DWORD sidenum = sidetemp[vnum[vnumat++]].b.first;
 		while (sidenum != NO_SIDE)
 		{
-			po->Sidedefs.Push(&sides[sidenum]);
-			AddPolyVert(vnum, DWORD(sides[sidenum].V2() - vertexes));
+			po->Sidedefs.Push(&level.sides[sidenum]);
+			AddPolyVert(vnum, DWORD(level.sides[sidenum].V2()->Index()));
 			sidenum = sidetemp[sidenum].b.next;
 		}
 	}
@@ -1534,7 +1522,7 @@ static void SpawnPolyobj (int index, int tag, int type)
 		po->bBlocked = false;
 		po->bHasPortals = 0;
 
-		side_t *sd = &sides[i];
+		side_t *sd = &level.sides[i];
 		
 		if (sd->linedef->special == Polyobj_StartLine &&
 			sd->linedef->args[0] == tag)
@@ -1570,14 +1558,14 @@ static void SpawnPolyobj (int index, int tag, int type)
 			i = KnownPolySides[ii];
 
 			if (i >= 0 &&
-				sides[i].linedef->special == Polyobj_ExplicitLine &&
-				sides[i].linedef->args[0] == tag)
+				level.sides[i].linedef->special == Polyobj_ExplicitLine &&
+				level.sides[i].linedef->args[0] == tag)
 			{
-				if (!sides[i].linedef->args[1])
+				if (!level.sides[i].linedef->args[1])
 				{
-					I_Error("SpawnPolyobj: Explicit line missing order number in poly %d, linedef %d.\n", tag, int(sides[i].linedef - lines));
+					I_Error("SpawnPolyobj: Explicit line missing order number in poly %d, linedef %d.\n", tag, level.sides[i].linedef->Index());
 				}
-				po->Sidedefs.Push (&sides[i]);
+				po->Sidedefs.Push (&level.sides[i]);
 			}
 		}
 		qsort(&po->Sidedefs[0], po->Sidedefs.Size(), sizeof(po->Sidedefs[0]), posicmp);
@@ -1776,11 +1764,11 @@ void PO_Init (void)
 		}
 	}
 	// clear all polyobj specials so that they do not obstruct using other lines.
-	for (int i = 0; i < numlines; i++)
+	for (auto &line : level.lines)
 	{
-		if (lines[i].special == Polyobj_ExplicitLine || lines[i].special == Polyobj_StartLine)
+		if (line.special == Polyobj_ExplicitLine || line.special == Polyobj_StartLine)
 		{
-			lines[i].special = 0;
+			line.special = 0;
 		}
 	}
 }
diff --git a/src/portal.cpp b/src/portal.cpp
index fa5c9fed7..abe442554 100644
--- a/src/portal.cpp
+++ b/src/portal.cpp
@@ -51,6 +51,7 @@
 #include "p_spec.h"
 #include "p_checkposition.h"
 #include "math/cmath.h"
+#include "g_levellocals.h"
 
 // simulation recurions maximum
 CVAR(Int, sv_portal_recursions, 4, CVAR_ARCHIVE|CVAR_SERVERINFO)
@@ -115,7 +116,7 @@ static void BuildBlockmap()
 
 			while (*list != -1)
 			{
-				line_t *ld = &lines[*list++];
+				line_t *ld = &level.lines[*list++];
 				FLinePortal *port = ld->getPortal();
 				if (port && port->mType != PORTT_VISUAL)
 				{
@@ -209,9 +210,9 @@ static line_t *FindDestination(line_t *src, int tag)
 
 		while ((lineno = it.Next()) >= 0)
 		{
-			if (&lines[lineno] != src)
+			if (&level.lines[lineno] != src)
 			{
-				return &lines[lineno];
+				return &level.lines[lineno];
 			}
 		}
 	}
@@ -290,7 +291,7 @@ void P_SpawnLinePortal(line_t* line)
 			if (port->mType == PORTT_INTERACTIVE && port->mAlign != PORG_ABSOLUTE)
 			{
 				// Due to the way z is often handled, these pose a major issue for parts of the code that needs to transparently handle interactive portals.
-				Printf(TEXTCOLOR_RED "Warning: z-offsetting not allowed for interactive portals. Changing line %d to teleport-portal!\n", int(line - lines));
+				Printf(TEXTCOLOR_RED "Warning: z-offsetting not allowed for interactive portals. Changing line %d to teleport-portal!\n", line->Index());
 				port->mType = PORTT_TELEPORT;
 			}
 		}
@@ -305,26 +306,26 @@ void P_SpawnLinePortal(line_t* line)
 
 		int mytag = tagManager.GetFirstLineID(line);
 
-		for (int i = 0; i < numlines; i++)
+		for (auto &ln : level.lines)
 		{
-			if (tagManager.GetFirstLineID(&lines[i]) == mytag && lines[i].args[0] == 1 && lines[i].special == Line_SetPortal)
+			if (tagManager.GetFirstLineID(&ln) == mytag && ln.args[0] == 1 && ln.special == Line_SetPortal)
 			{
 				line->portalindex = linePortals.Reserve(1);
 				FLinePortal *port = &linePortals.Last();
 
 				memset(port, 0, sizeof(FLinePortal));
 				port->mOrigin = line;
-				port->mDestination = &lines[i];
+				port->mDestination = &ln;
 				port->mType = PORTT_LINKED;
 				port->mAlign = PORG_ABSOLUTE;
 				port->mDefFlags = PORTF_TYPEINTERACTIVE;
 
 				// we need to create the backlink here, too.
-				lines[i].portalindex = linePortals.Reserve(1);
+				ln.portalindex = linePortals.Reserve(1);
 				port = &linePortals.Last();
 
 				memset(port, 0, sizeof(FLinePortal));
-				port->mOrigin = &lines[i];
+				port->mOrigin = &ln;
 				port->mDestination = line;
 				port->mType = PORTT_LINKED;
 				port->mAlign = PORG_ABSOLUTE;
@@ -473,7 +474,7 @@ bool P_ChangePortal(line_t *ln, int thisid, int destid)
 	bool res = false;
 	while ((lineno = it.Next()) >= 0)
 	{
-		res |= ChangePortalLine(&lines[lineno], destid);
+		res |= ChangePortalLine(&level.lines[lineno], destid);
 	}
 	return res;
 }
@@ -868,13 +869,13 @@ static void AddDisplacementForPortal(FLinePortal *portal)
 	int othergroup = portal->mDestination->frontsector->PortalGroup;
 	if (thisgroup == othergroup)
 	{
-		Printf("Portal between lines %d and %d has both sides in same group\n", int(portal->mOrigin-lines), int(portal->mDestination-lines));
+		Printf("Portal between lines %d and %d has both sides in same group\n", portal->mOrigin->Index(), portal->mDestination->Index());
 		portal->mType = linePortals[portal->mDestination->portalindex].mType = PORTT_TELEPORT;
 		return;
 	}
 	if (thisgroup <= 0 || thisgroup >= Displacements.size || othergroup <= 0 || othergroup >= Displacements.size)
 	{
-		Printf("Portal between lines %d and %d has invalid group\n", int(portal->mOrigin - lines), int(portal->mDestination - lines));
+		Printf("Portal between lines %d and %d has invalid group\n", portal->mOrigin->Index(), portal->mDestination->Index());
 		portal->mType = linePortals[portal->mDestination->portalindex].mType = PORTT_TELEPORT;
 		return;
 	}
@@ -889,7 +890,7 @@ static void AddDisplacementForPortal(FLinePortal *portal)
 	{
 		if (disp.pos != portal->mDisplacement)
 		{
-			Printf("Portal between lines %d and %d has displacement mismatch\n", int(portal->mOrigin - lines), int(portal->mDestination - lines));
+			Printf("Portal between lines %d and %d has displacement mismatch\n", portal->mOrigin->Index(), portal->mDestination->Index());
 			portal->mType = linePortals[portal->mDestination->portalindex].mType = PORTT_TELEPORT;
 			return;
 		}
@@ -1057,11 +1058,11 @@ void P_CreateLinkedPortals()
 				bogus = true;
 			}
 			// mark everything that connects to a one-sided line
-			for (int i = 0; i < numlines; i++)
+			for (auto &line : level.lines)
 			{
-				if (lines[i].backsector == NULL && lines[i].frontsector->PortalGroup == 0)
+				if (line.backsector == nullptr && line.frontsector->PortalGroup == 0)
 				{
-					CollectSectors(-1, lines[i].frontsector);
+					CollectSectors(-1, line.frontsector);
 				}
 			}
 			// and now print a message for everything that still wasn't processed.
diff --git a/src/posix/sdl/i_main.cpp b/src/posix/sdl/i_main.cpp
index ca704340d..90b11ef25 100644
--- a/src/posix/sdl/i_main.cpp
+++ b/src/posix/sdl/i_main.cpp
@@ -52,6 +52,7 @@
 #include "version.h"
 #include "w_wad.h"
 #include "g_level.h"
+#include "g_levellocals.h"
 #include "r_state.h"
 #include "cmdlib.h"
 #include "r_utility.h"
diff --git a/src/r_defs.h b/src/r_defs.h
index 8a10a9faf..e8af4ea68 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -130,11 +130,13 @@ struct vertex_t
 		return FLOAT2FIXED(p.Y);
 	}
 
-	DVector2 fPos()
+	DVector2 fPos() const
 	{
 		return p;
 	}
 
+	int Index() const;
+
 	angle_t viewangle;	// precalculated angle for clipping
 	int angletime;		// recalculation time for view angle
 	bool dirty;			// something has changed and needs to be recalculated
@@ -655,7 +657,7 @@ public:
 	double FindLowestCeilingPoint(vertex_t **v) const;
 	double FindHighestFloorPoint(vertex_t **v) const;
 	void RemoveForceField();
-	int Index() const { return int(this - &level.sectors[0]); }
+	int Index() const;
 
 	void AdjustFloorClip () const;
 	void SetColor(int r, int g, int b, int desat);
@@ -1157,7 +1159,7 @@ struct side_t
 	WORD		TexelLength;
 	SWORD		Light;
 	BYTE		Flags;
-	int			Index;		// needed to access custom UDMF fields which are stored in loading order.
+	int			UDMFIndex;		// needed to access custom UDMF fields which are stored in loading order.
 
 	int GetLightLevel (bool foggy, int baselight, bool is3dlight=false, int *pfakecontrast_usedbygzdoom=NULL) const;
 
@@ -1265,6 +1267,8 @@ struct side_t
 	vertex_t *V1() const;
 	vertex_t *V2() const;
 
+	int Index() const;
+
 	//For GL
 	FLightNode * lighthead;				// all blended lights that may affect this wall
 
@@ -1336,8 +1340,20 @@ struct line_t
 	{
 		return portalindex >= linePortals.Size() ? 0 : linePortals[portalindex].mAlign;
 	}
+
+	int Index() const;
 };
 
+inline vertex_t *side_t::V1() const
+{
+	return this == linedef->sidedef[0] ? linedef->v1 : linedef->v2;
+}
+
+inline vertex_t *side_t::V2() const
+{
+	return this == linedef->sidedef[0] ? linedef->v2 : linedef->v1;
+}
+
 // phares 3/14/98
 //
 // Sector list node showing all sectors an object appears in.
@@ -1401,12 +1417,6 @@ struct seg_t
 	float			sidefrac;		// relative position of seg's ending vertex on owning sidedef
 };
 
-struct glsegextra_t
-{
-	DWORD		 PartnerSeg;
-	subsector_t *Subsector;
-};
-
 extern seg_t *segs;
 
 
diff --git a/src/r_sky.cpp b/src/r_sky.cpp
index f29929c26..89a2bc44c 100644
--- a/src/r_sky.cpp
+++ b/src/r_sky.cpp
@@ -34,6 +34,7 @@
 #include "r_utility.h"
 #include "v_text.h"
 #include "gi.h"
+#include "g_levellocals.h"
 
 //
 // sky mapping
diff --git a/src/r_state.h b/src/r_state.h
index c3fa03636..7151c0441 100644
--- a/src/r_state.h
+++ b/src/r_state.h
@@ -42,10 +42,7 @@ extern "C" int			viewheight;
 extern TArray<spritedef_t> sprites;
 extern DWORD NumStdSprites;
 
-extern int				numvertexes;
-extern vertex_t*		vertexes;
-extern int				numvertexdatas;
-extern vertexdata_t*		vertexdatas;
+extern TArray<vertexdata_t> vertexdatas;
 
 extern int				numsegs;
 extern seg_t*			segs;
@@ -56,12 +53,6 @@ extern subsector_t* 	subsectors;
 extern int				numnodes;
 extern node_t*			nodes;
 
-extern int				numlines;
-extern line_t*			lines;
-
-extern int				numsides;
-extern side_t*			sides;
-
 extern TArray<zone_t>	Zones;
 
 extern node_t * 		gamenodes;
diff --git a/src/s_advsound.cpp b/src/s_advsound.cpp
index 083e0eeef..d2c40109a 100644
--- a/src/s_advsound.cpp
+++ b/src/s_advsound.cpp
@@ -52,6 +52,7 @@
 #include "d_player.h"
 #include "serializer.h"
 #include "v_text.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/s_sndseq.cpp b/src/s_sndseq.cpp
index 28786ef8f..31ed314b7 100644
--- a/src/s_sndseq.cpp
+++ b/src/s_sndseq.cpp
@@ -29,6 +29,7 @@
 #include "g_level.h"
 #include "serializer.h"
 #include "d_player.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/s_sound.cpp b/src/s_sound.cpp
index a37182e20..3888ee3dc 100644
--- a/src/s_sound.cpp
+++ b/src/s_sound.cpp
@@ -53,6 +53,7 @@
 #include "serializer.h"
 #include "d_player.h"
 #include "r_state.h"
+#include "g_levellocals.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/scripting/thingdef_data.cpp b/src/scripting/thingdef_data.cpp
index 2e9654607..46485b226 100644
--- a/src/scripting/thingdef_data.cpp
+++ b/src/scripting/thingdef_data.cpp
@@ -49,6 +49,7 @@
 #include "gstrings.h"
 #include "zstring.h"
 #include "d_event.h"
+#include "g_levellocals.h"
 
 static TArray<FPropertyInfo*> properties;
 static TArray<AFuncDesc> AFTable;
@@ -716,18 +717,31 @@ void InitThingdef()
 	auto secplanestruct = NewNativeStruct("Secplane", nullptr);
 	secplanestruct->Size = sizeof(secplane_t);
 	secplanestruct->Align = alignof(secplane_t);
+
 	auto sectorstruct = NewNativeStruct("Sector", nullptr);
 	sectorstruct->Size = sizeof(sector_t);
 	sectorstruct->Align = alignof(sector_t);
 
+	auto linestruct = NewNativeStruct("Line", nullptr);
+	linestruct->Size = sizeof(line_t);
+	linestruct->Align = alignof(line_t);
+
+	auto sidestruct = NewNativeStruct("Side", nullptr);
+	sidestruct->Size = sizeof(side_t);
+	sidestruct->Align = alignof(side_t);
+
+	auto vertstruct = NewNativeStruct("Vertex", nullptr);
+	vertstruct->Size = sizeof(vertex_t);
+	vertstruct->Align = alignof(vertex_t);
+
 
 	// set up the lines array in the sector struct. This is a bit messy because the type system is not prepared to handle a pointer to an array of pointers to a native struct even remotely well...
 	// As a result, the size has to be set to something large and arbritrary because it can change between maps. This will need some serious improvement when things get cleaned up.
-	sectorstruct->AddNativeField("lines", NewPointer(NewResizableArray(NewPointer(NewNativeStruct("line", nullptr), false)), false), myoffsetof(sector_t, Lines), VARF_Native);
+	sectorstruct->AddNativeField("lines", NewPointer(NewResizableArray(NewPointer(linestruct, false)), false), myoffsetof(sector_t, Lines), VARF_Native);
 
-	// add the sector planes. These are value items of native structs so they have to be done here.
-	sectorstruct->AddNativeField("ceilingplane", secplanestruct, myoffsetof(sector_t, ceilingplane), VARF_Native);
-	sectorstruct->AddNativeField("floorplane", secplanestruct, myoffsetof(sector_t, floorplane), VARF_Native);
+	// add the sector planes. These are value items of native structs so they have to be done here. Write access should be through functions only to allow later optimization inside the renderer.
+	sectorstruct->AddNativeField("ceilingplane", secplanestruct, myoffsetof(sector_t, ceilingplane), VARF_Native|VARF_ReadOnly);
+	sectorstruct->AddNativeField("floorplane", secplanestruct, myoffsetof(sector_t, floorplane), VARF_Native|VARF_ReadOnly);
 
 
 
@@ -747,6 +761,9 @@ void InitThingdef()
 
 	// Add the sector array to LevelLocals.
 	lstruct->AddNativeField("sectors", NewPointer(NewResizableArray(sectorstruct), false), myoffsetof(FLevelLocals, sectors), VARF_Native);
+	lstruct->AddNativeField("lines", NewPointer(NewResizableArray(linestruct), false), myoffsetof(FLevelLocals, lines), VARF_Native);
+	lstruct->AddNativeField("sides", NewPointer(NewResizableArray(sidestruct), false), myoffsetof(FLevelLocals, sides), VARF_Native);
+	lstruct->AddNativeField("vertexes", NewPointer(NewResizableArray(vertstruct), false), myoffsetof(FLevelLocals, vertexes), VARF_Native|VARF_ReadOnly);
 
 	// set up a variable for the DEH data
 	PStruct *dstruct = NewNativeStruct("DehInfo", nullptr);
diff --git a/src/scripting/thingdef_properties.cpp b/src/scripting/thingdef_properties.cpp
index e54a00963..c4c44a709 100644
--- a/src/scripting/thingdef_properties.cpp
+++ b/src/scripting/thingdef_properties.cpp
@@ -73,6 +73,7 @@
 #include "a_ammo.h"
 #include "a_health.h"
 #include "a_keys.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
diff --git a/src/scripting/vm/vm.h b/src/scripting/vm/vm.h
index fdf5f3c9f..2e98e865e 100644
--- a/src/scripting/vm/vm.h
+++ b/src/scripting/vm/vm.h
@@ -209,6 +209,9 @@ public:
 	void MaybePrintMessage();
 };
 
+// This must be a separate function because the VC compiler would otherwise allocate memory on the stack for every separate instance of the exception object that may get thrown.
+void ThrowAbortException(EVMAbortException reason, const char *moreinfo, ...);
+
 enum EVMOpMode
 {
 	MODE_ASHIFT		= 0,
diff --git a/src/scripting/vm/vmexec.cpp b/src/scripting/vm/vmexec.cpp
index 3183edcfb..1ad4e3256 100644
--- a/src/scripting/vm/vmexec.cpp
+++ b/src/scripting/vm/vmexec.cpp
@@ -44,9 +44,7 @@
 extern cycle_t VMCycles[10];
 extern int VMCalls[10];
 
-// This must be a separate function because the VC compiler would otherwise allocate memory on the stack for every separate instance of the exception object that may get thrown.
-void ThrowAbortException(EVMAbortException reason, const char *moreinfo, ...);
-// intentionally implemented in a different source file tp prevent inlining.
+// intentionally implemented in a different source file to prevent inlining.
 void ThrowVMException(VMException *x);
 
 #define IMPLEMENT_VMEXEC
diff --git a/src/scripting/zscript/zcc_compile.cpp b/src/scripting/zscript/zcc_compile.cpp
index 9684ec924..52cbc1d65 100644
--- a/src/scripting/zscript/zcc_compile.cpp
+++ b/src/scripting/zscript/zcc_compile.cpp
@@ -2336,6 +2336,7 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 			sym->Variants[0].Implementation->DefaultArgs = std::move(argdefaults);
 		}
 
+		PClass *clstype = static_cast<PClass *>(c->Type());
 		if (varflags & VARF_Virtual)
 		{
 			if (sym->Variants[0].Implementation == nullptr)
@@ -2349,7 +2350,6 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 			}
 			if (forclass)
 			{
-				PClass *clstype = static_cast<PClass *>(c->Type());
 				int vindex = clstype->FindVirtualIndex(sym->SymbolName, sym->Variants[0].Proto);
 				// specifying 'override' is necessary to prevent one of the biggest problem spots with virtual inheritance: Mismatching argument types.
 				if (varflags & VARF_Override)
@@ -2383,6 +2383,14 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 				Error(p, "Virtual functions can only be defined for classes");
 			}
 		}
+		else if (forclass)
+		{
+			int vindex = clstype->FindVirtualIndex(sym->SymbolName, sym->Variants[0].Proto);
+			if (vindex != -1)
+			{
+				Error(f, "Function %s attempts to override parent function without 'override' qualifier", FName(f->Name).GetChars());
+			}
+		}
 	}
 }
 
diff --git a/src/serializer.cpp b/src/serializer.cpp
index 7c48f9b1e..5154b0700 100644
--- a/src/serializer.cpp
+++ b/src/serializer.cpp
@@ -64,6 +64,7 @@
 #include "doomerrors.h"
 #include "v_text.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 char nulspace[1024 * 1024 * 4];
 bool save_full = false;	// for testing. Should be removed afterward.
@@ -1458,7 +1459,7 @@ template<> FSerializer &Serialize(FSerializer &arc, const char *key, const FPoly
 
 template<> FSerializer &Serialize(FSerializer &arc, const char *key, side_t *&value, side_t **defval)
 {
-	return SerializePointer(arc, key, value, defval, sides);
+	return SerializePointer(arc, key, value, defval, &level.sides[0]);
 }
 
 template<> FSerializer &Serialize(FSerializer &arc, const char *key, sector_t *&value, sector_t **defval)
@@ -1478,12 +1479,12 @@ template<> FSerializer &Serialize(FSerializer &arc, const char *key, player_t *&
 
 template<> FSerializer &Serialize(FSerializer &arc, const char *key, line_t *&value, line_t **defval)
 {
-	return SerializePointer(arc, key, value, defval, lines);
+	return SerializePointer(arc, key, value, defval, &level.lines[0]);
 }
 
 template<> FSerializer &Serialize(FSerializer &arc, const char *key, vertex_t *&value, vertex_t **defval)
 {
-	return SerializePointer(arc, key, value, defval, vertexes);
+	return SerializePointer(arc, key, value, defval, &level.vertexes[0]);
 }
 
 //==========================================================================
diff --git a/src/serializer.h b/src/serializer.h
index 4797a4bce..e4dc8f226 100644
--- a/src/serializer.h
+++ b/src/serializer.h
@@ -15,10 +15,6 @@ struct usercmd_t;
 struct FWriter;
 struct FReader;
 
-extern TArray<sector_t>	loadsectors;
-extern TArray<line_t>	loadlines;
-extern TArray<side_t>	loadsides;
-
 inline bool nullcmp(const void *buffer, size_t length)
 {
 	const char *p = (const char *)buffer;
diff --git a/src/st_stuff.cpp b/src/st_stuff.cpp
index 31cf9b3a7..632eaadf8 100644
--- a/src/st_stuff.cpp
+++ b/src/st_stuff.cpp
@@ -30,6 +30,7 @@
 #include "d_net.h"
 #include "doomstat.h"
 #include "g_level.h"
+#include "g_levellocals.h"
 
 EXTERN_CVAR (Bool, ticker);
 EXTERN_CVAR (Bool, noisedebug);
diff --git a/src/statistics.cpp b/src/statistics.cpp
index 92a459e15..e96f10327 100644
--- a/src/statistics.cpp
+++ b/src/statistics.cpp
@@ -71,6 +71,7 @@
 #include "p_lnspec.h"
 #include "m_crc32.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 CVAR(Int, savestatistics, 0, CVAR_ARCHIVE|CVAR_GLOBALCONFIG)
 CVAR(String, statfile, "zdoomstat.txt", CVAR_ARCHIVE|CVAR_GLOBALCONFIG)
diff --git a/src/tarray.h b/src/tarray.h
index 7e6affb97..3ee1c5cb9 100644
--- a/src/tarray.h
+++ b/src/tarray.h
@@ -553,6 +553,13 @@ public:
 		this->Count = 0;
 		this->Array = NULL;
 	}
+	TStaticArray(TStaticArray<T> &&other)
+	{
+		this->Array = other.Array;
+		this->Count = other.Count;
+		other.Array = nullptr;
+		other.Count = 0;
+	}
 	// This is not supposed to be copyable.
 	TStaticArray(const TStaticArray<T> &other) = delete;
 
@@ -564,7 +571,7 @@ public:
 	{
 		if (this->Array) delete[] this->Array;
 		this->Count = 0;
-		this->Array = NULL;
+		this->Array = nullptr;
 	}
 	void Alloc(unsigned int amount)
 	{
@@ -573,6 +580,21 @@ public:
 		this->Array = new T[amount];
 		this->Count = amount;
 	}
+	TStaticArray &operator=(const TStaticArray &other)
+	{
+		Alloc(other.Size());
+		memcpy(this->Array, other.Array, this->Count * sizeof(T));
+		return *this;
+	}
+	TStaticArray &operator=(TStaticArray &&other)
+	{
+		if (this->Array) delete[] this->Array;
+		this->Array = other.Array;
+		this->Count = other.Count;
+		other.Array = nullptr;
+		other.Count = 0;
+		return *this;
+	}
 };
 
 
diff --git a/src/v_draw.cpp b/src/v_draw.cpp
index 07c3d2a13..a285fdd1e 100644
--- a/src/v_draw.cpp
+++ b/src/v_draw.cpp
@@ -61,6 +61,7 @@
 #include "d_net.h"
 #include "colormatcher.h"
 #include "r_data/colormaps.h"
+#include "g_levellocals.h"
 
 CUSTOM_CVAR(Int, uiscale, 2, CVAR_ARCHIVE | CVAR_NOINITCALL)
 {
diff --git a/src/v_palette.cpp b/src/v_palette.cpp
index aa39ba791..4f4c9cb18 100644
--- a/src/v_palette.cpp
+++ b/src/v_palette.cpp
@@ -56,6 +56,7 @@
 #include "x86.h"
 #include "colormatcher.h"
 #include "v_palette.h"
+#include "g_levellocals.h"
 #include "r_data/colormaps.h"
 
 FPalette GPalette;
diff --git a/src/wi_stuff.cpp b/src/wi_stuff.cpp
index 12ca10e32..eb1c7d2fa 100644
--- a/src/wi_stuff.cpp
+++ b/src/wi_stuff.cpp
@@ -52,6 +52,7 @@
 #include "templates.h"
 #include "gstrings.h"
 #include "cmdlib.h"
+#include "g_levellocals.h"
 
 // States for the intermission
 typedef enum
diff --git a/src/win32/i_main.cpp b/src/win32/i_main.cpp
index 2a99f4364..14c4791c6 100644
--- a/src/win32/i_main.cpp
+++ b/src/win32/i_main.cpp
@@ -81,6 +81,7 @@
 #include "g_level.h"
 #include "doomstat.h"
 #include "r_utility.h"
+#include "g_levellocals.h"
 
 #include "stats.h"
 #include "st_start.h"
diff --git a/wadsrc/static/zscript/base.txt b/wadsrc/static/zscript/base.txt
index 673257a3c..232becccc 100644
--- a/wadsrc/static/zscript/base.txt
+++ b/wadsrc/static/zscript/base.txt
@@ -190,6 +190,56 @@ struct Vertex native
 	native readonly Vector2 p;
 }
 
+struct Side
+{
+	enum ETexpart
+	{
+		top=0,
+		mid=1,
+		bottom=2
+	};
+	
+	enum EWallFlags
+	{
+		WALLF_ABSLIGHTING	 = 1,	// Light is absolute instead of relative
+		WALLF_NOAUTODECALS	 = 2,	// Do not attach impact decals to this wall
+		WALLF_NOFAKECONTRAST = 4,	// Don't do fake contrast for this wall in side_t::GetLightLevel
+		WALLF_SMOOTHLIGHTING = 8,   // Similar to autocontrast but applies to all angles.
+		WALLF_CLIP_MIDTEX	 = 16,	// Like the line counterpart, but only for this side.
+		WALLF_WRAP_MIDTEX	 = 32,	// Like the line counterpart, but only for this side.
+		WALLF_POLYOBJ		 = 64,	// This wall belongs to a polyobject.
+		WALLF_LIGHT_FOG      = 128,	// This wall's Light is used even in fog.
+	};
+
+	native Sector	sector;			// Sector the SideDef is facing.
+	//DBaseDecal*	AttachedDecals;	// [RH] Decals bound to the wall
+	native Line		linedef;
+	native int16	Light;
+	native uint8	Flags;
+
+	native TextureID GetTexture(int which);
+	native void SetTexture(int which, TextureID tex);
+	native void SetTextureXOffset(int which, double offset);
+	native double GetTextureXOffset(int which);
+	native void AddTextureXOffset(int which, double delta);
+	native void SetTextureYOffset(int which, double offset);
+	native double GetTextureYOffset(int which);
+	native void AddTextureYOffset(int which, double delta);
+	native void SetTextureXScale(int which, double scale);
+	native double GetTextureXScale(int which);
+	native void MultiplyTextureXScale(int which, double delta);
+	native void SetTextureYScale(int which, double scale);
+	native double GetTextureYScale(int which);
+	native void MultiplyTextureYScale(int which, double delta);
+	//native DInterpolation *SetInterpolation(int position);
+	//native void StopInterpolation(int position);
+
+	native Vertex V1();
+	native Vertex V2();
+
+	native int Index();
+};
+
 struct Line native
 {
 	enum ELineFlags
@@ -226,7 +276,7 @@ struct Line native
 	};
 
 
-	//native readonly vertex		v1, v2;		// vertices, from v1 to v2
+	native readonly vertex			v1, v2;		// vertices, from v1 to v2
 	native readonly Vector2			delta;		// precalculated v2 - v1 for side checking
 	native uint						flags;
 	native uint						activation;	// activation type
@@ -239,6 +289,13 @@ struct Line native
 	native int 						validcount;	// if == validcount, already checked
 	native int						locknumber;	// [Dusk] lock number for special
 	native readonly uint			portalindex;
+	native readonly uint			portaltransferred;
+	
+	native bool isLinePortal();
+	native bool isVisualPortal();
+	native Line getPortalDestination();
+	native int getPortalAlignment();
+	native int Index();
 }
 
 struct SecPlane native
@@ -295,6 +352,12 @@ struct Sector native
 	//SectorEffect ceilingdata;	
 	//SectorEffect lightingdata;
 
+	enum EPlane
+	{
+		floor,
+		ceiling
+	};
+	
 	enum EInterpolationType
 	{
 		CeilingMove,
@@ -378,6 +441,7 @@ struct Sector native
 
 	native readonly int			sectornum;
 
+	native int Index();
 
 	native double, Sector, F3DFloor NextHighestCeilingAt(double x, double y, double bottomz, double topz, int flags = 0);
 	native double, Sector, F3DFloor NextLowestFloorAt(double x, double y, double z, int flags = 0, double steph = 0);
diff --git a/wadsrc/static/zscript/heretic/hereticartifacts.txt b/wadsrc/static/zscript/heretic/hereticartifacts.txt
index 20f52a2c9..3b7f14ad8 100644
--- a/wadsrc/static/zscript/heretic/hereticartifacts.txt
+++ b/wadsrc/static/zscript/heretic/hereticartifacts.txt
@@ -66,7 +66,7 @@ Class ArtiTomeOfPower : PowerupGiver
 		Loop;
 	}
 	
-	bool Use (bool pickup)
+	override bool Use (bool pickup)
 	{
 		Playerinfo p = Owner.player;
 		if (p && p.morphTics && (p.MorphStyle & MRF_UNDOBYTOMEOFPOWER))
diff --git a/wadsrc/static/zscript/heretic/weaponblaster.txt b/wadsrc/static/zscript/heretic/weaponblaster.txt
index 913abffdb..e7e1e92b5 100644
--- a/wadsrc/static/zscript/heretic/weaponblaster.txt
+++ b/wadsrc/static/zscript/heretic/weaponblaster.txt
@@ -220,7 +220,7 @@ class Ripper : Actor
 		Stop;
 	}
 	
-	int DoSpecialDamage (Actor target, int damage, Name damagetype)
+	override int DoSpecialDamage (Actor target, int damage, Name damagetype)
 	{
 		if (target is "Ironlich")
 		{ // Less damage to Ironlich bosses
diff --git a/wadsrc/static/zscript/heretic/weaponphoenix.txt b/wadsrc/static/zscript/heretic/weaponphoenix.txt
index eb75acb1d..558a257cd 100644
--- a/wadsrc/static/zscript/heretic/weaponphoenix.txt
+++ b/wadsrc/static/zscript/heretic/weaponphoenix.txt
@@ -311,7 +311,7 @@ class PhoenixFX2 : Actor
 	}
 	
 
-	int DoSpecialDamage (Actor target, int damage, Name damagetype)
+	override int DoSpecialDamage (Actor target, int damage, Name damagetype)
 	{
 		if (target.player && Random[PhoenixFX2]() < 128)
 		{ // Freeze player for a bit
diff --git a/wadsrc/static/zscript/heretic/weaponskullrod.txt b/wadsrc/static/zscript/heretic/weaponskullrod.txt
index a8d77e1d8..da959f7ae 100644
--- a/wadsrc/static/zscript/heretic/weaponskullrod.txt
+++ b/wadsrc/static/zscript/heretic/weaponskullrod.txt
@@ -402,7 +402,7 @@ class RainPillar : Actor
 
 	// Rain pillar 1 ------------------------------------------------------------
 
-	int DoSpecialDamage (Actor target, int damage, Name damagetype)
+	override int DoSpecialDamage (Actor target, int damage, Name damagetype)
 	{
 		if (target.bBoss)
 		{ // Decrease damage for bosses
diff --git a/wadsrc/static/zscript/hexen/heresiarch.txt b/wadsrc/static/zscript/hexen/heresiarch.txt
index db4860c34..f89d2fb83 100644
--- a/wadsrc/static/zscript/hexen/heresiarch.txt
+++ b/wadsrc/static/zscript/hexen/heresiarch.txt
@@ -112,7 +112,7 @@ class Heresiarch : Actor
 		Stop;
 	}
 
-	void Die (Actor source, Actor inflictor, int dmgflags)
+	override void Die (Actor source, Actor inflictor, int dmgflags)
 	{
 		// The heresiarch just executes a script instead of a special upon death
 		int script = special;
@@ -698,8 +698,8 @@ class SorcBall2 : SorcBall
 
 		Actor parent = target;
 		Actor mo = Spawn("SorcFX2", Pos + (0, 0, parent.Floorclip + Heresiarch.SORC_DEFENSE_HEIGHT), ALLOW_REPLACE);
-		bReflective = true;
-		bInvulnerable = true;
+		parent.bReflective = true;
+		parent.bInvulnerable = true;
 		parent.args[0] = Heresiarch.SORC_DEFENSE_TIME;
 		if (mo) mo.target = parent;
 	}
diff --git a/wadsrc/static/zscript/shared/setcolor.txt b/wadsrc/static/zscript/shared/setcolor.txt
index 18105ef54..2d9d3be57 100644
--- a/wadsrc/static/zscript/shared/setcolor.txt
+++ b/wadsrc/static/zscript/shared/setcolor.txt
@@ -28,7 +28,7 @@ class FadeSetter : Actor
 		RenderStyle "None";
 	}
 	
-	void PostBeginPlay()
+	override void PostBeginPlay()
 	{
 		Super.PostBeginPlay();
 		CurSector.SetFade(color(args[0], args[1], args[2]));
diff --git a/wadsrc/static/zscript/strife/weapongrenade.txt b/wadsrc/static/zscript/strife/weapongrenade.txt
index 7a775c57b..21e568313 100644
--- a/wadsrc/static/zscript/strife/weapongrenade.txt
+++ b/wadsrc/static/zscript/strife/weapongrenade.txt
@@ -241,7 +241,7 @@ class PhosphorousFire : Actor
 		Stop;
 	}
 	
-	int DoSpecialDamage (Actor target, int damage, Name damagetype)
+	override int DoSpecialDamage (Actor target, int damage, Name damagetype)
 	{
 		if (target.bNoBlood)
 		{