diff --git a/source/build/include/build.h b/source/build/include/build.h
index 9421b59bd..e523bde57 100644
--- a/source/build/include/build.h
+++ b/source/build/include/build.h
@@ -628,7 +628,7 @@ int32_t md_definehud (int32_t modelid, int32_t tilex, vec3f_t add,
 int32_t md_undefinetile(int32_t tile);
 int32_t md_undefinemodel(int32_t modelid);
 
-int32_t loaddefinitionsfile(const char *fn, bool loadadds = false);
+int32_t loaddefinitionsfile(const char *fn, bool loadadds = false, bool cumulative = false);
 
 #ifdef USE_OPENGL
 # include "polymost.h"
diff --git a/source/build/include/scriptfile.h b/source/build/include/scriptfile.h
index c7aaf4fa8..5b742cd29 100644
--- a/source/build/include/scriptfile.h
+++ b/source/build/include/scriptfile.h
@@ -113,12 +113,6 @@ inline void scriptfile_close(scriptfile *sf)
 	delete sf;
 }
 
-inline int32_t scriptfile_addsymbolvalue(scriptfile *sf, char const *name, int32_t val)
-{
-	sf->AddSymbol(name, val);
-	return 1;
-}
-
 typedef struct
 {
     const char *text;
diff --git a/source/build/src/defs.cpp b/source/build/src/defs.cpp
index 9b7993666..91c2eac86 100644
--- a/source/build/src/defs.cpp
+++ b/source/build/src/defs.cpp
@@ -2917,7 +2917,7 @@ static int32_t defsparser(scriptfile *script)
                 break;
 
             FStringf name("%s.%s", resName.GetChars(), resType.GetChars());
-            fileSystem.CreatePathlessCopy(resName, resID, 0);
+            fileSystem.CreatePathlessCopy(name, resID, 0);
         }
         break;
 
@@ -2930,34 +2930,44 @@ static int32_t defsparser(scriptfile *script)
     return 0;
 }
 
-
-int32_t loaddefinitionsfile(const char *fn, bool loadadds)
+int32_t loaddefinitionsfile(const char *fn, bool loadadds, bool cumulative)
 {
-    scriptfile *script;
-
-    script = scriptfile_fromfile(fn);
-
-    if (script)
+    bool done = false;
+    auto parseit = [&](int lump)
     {
-        Printf(PRINT_NONOTIFY, "Loading \"%s\"\n",fn);
+        FScanner sc;
+        sc.OpenLumpNum(lump);
+        sc.SetNoOctals(true);
+        sc.SetNoFatalErrors(true);
+        defsparser(&sc);
+        done = true;
+        Printf(PRINT_NONOTIFY, "\n");
+    };
 
-        defsparser(script);
+    if (!cumulative)
+    {
+        int lump = fileSystem.FindFile(fn);
+        if (lump >= 0)
+        {
+            Printf(PRINT_NONOTIFY, "Loading \"%s\"\n", fn);
+            parseit(lump);
+    }
+    }
+    else
+    {
+        int lump, lastlump = 0;
+        while ((lump = fileSystem.FindLumpFullName(fn, &lastlump)) >= 0)
+        {
+            Printf(PRINT_NONOTIFY, "Loading \"%s\"\n", fileSystem.GetFileFullPath(lump).GetChars());
+            parseit(lump);
+        }
     }
 
     if (userConfig.AddDefs && loadadds) for (auto& m : *userConfig.AddDefs)
 	{
 		Printf("Loading module \"%s\"\n",m.GetChars());
-        defsparser_include(m, NULL, NULL); // Q: should we let the external script see our symbol table?
+        defsparser_include(m, nullptr, nullptr); // Q: should we let the external script see our symbol table?
+        Printf(PRINT_NONOTIFY, "\n");
 	}
-
-    if (script)
-        scriptfile_close(script);
-
-    if (!script) return -1;
-
-    Printf(PRINT_NONOTIFY, "\n");
-
     return 0;
 }
-
-// vim:ts=4:
diff --git a/source/common/filesystem/filesystem.cpp b/source/common/filesystem/filesystem.cpp
index 0ea4ac7a6..dae98edf5 100644
--- a/source/common/filesystem/filesystem.cpp
+++ b/source/common/filesystem/filesystem.cpp
@@ -76,14 +76,14 @@ struct FileSystem::LumpRecord
 			shortName.String[8] = 0;
 			longName = "";
 			Namespace = lump->GetNamespace();
-			resourceId = 0;
+			resourceId = -1;
 		}
 		else if ((lump->Flags & LUMPF_EMBEDDED) || !lump->getName() || !*lump->getName())
 		{
 			shortName.qword = 0;
 			longName = "";
 			Namespace = ns_hidden;
-			resourceId = 0;
+			resourceId = -1;
 		}
 		else
 		{
diff --git a/source/core/gamecontrol.cpp b/source/core/gamecontrol.cpp
index e5e5410f5..e8736bf98 100644
--- a/source/core/gamecontrol.cpp
+++ b/source/core/gamecontrol.cpp
@@ -361,7 +361,7 @@ void UserConfig::ProcessOptions()
 
 	static const char* defs[] = { "-def", "-h", nullptr };
 	Args->CollectFiles("-def", defs, ".def");
-	DefaultDef = Args->CheckValue("-def");
+	UserDef = Args->CheckValue("-def");
 
 	if (DefaultCon.IsEmpty())
 	{
@@ -1323,27 +1323,50 @@ void DrawCrosshair(int deftile, int health, double xdelta, double ydelta, double
 
 void LoadDefinitions()
 {
-	loaddefinitionsfile("engine/engine.def");	// Internal stuff that is required.
-
-	const char* defsfile = G_DefFile();
-
 	cycle_t deftimer;
 	deftimer.Reset();
 	deftimer.Clock();
-	if (!loaddefinitionsfile(defsfile, true))
+	const char* loaded = nullptr;
+
+	const char* defsfile = G_DefFile();
+	FString razedefsfile = defsfile;
+	razedefsfile.Substitute(".def", "-raze.def");
+
+	loaddefinitionsfile("engine/engine.def", false);	// Internal stuff that is required.
+
+	// check what we have.
+	// user .defs override the default ones and are not cumulative.
+	// if we fine even one Raze-specific file, all of those will be loaded cumulatively.
+	// otherwise the default rules inherited from older ports apply.
+	if (userConfig.UserDef.IsNotEmpty())
+	{
+		if (!loaddefinitionsfile(userConfig.UserDef, true, false)) loaded = userConfig.UserDef;
+	}
+	else
+	{
+		if (fileSystem.FileExists(razedefsfile))
+		{
+			if (!loaddefinitionsfile(razedefsfile, true, true)) loaded = razedefsfile;
+		}
+		else
+		{
+			if (!loaddefinitionsfile(defsfile, true, false)) loaded = defsfile;
+		}
+	}
+	
+	if (loaded)
 	{
 		deftimer.Unclock();
-		Printf(PRINT_NONOTIFY, "Definitions file \"%s\" loaded in %.3f ms.\n", defsfile, deftimer.TimeMS());
+		DPrintf(DMSG_SPAMMY, "Definitions file \"%s\" loaded, %f ms.\n", loaded, deftimer.TimeMS());
 	}
 	userConfig.AddDefs.reset();
 
-	// load the widescreen replacements last so that they do not clobber the CRC for the original items so that mod-side replacement are picked up.
+	// load the widescreen replacements last. This ensures that mods still get the correct CRCs for their own tile replacements.
 	if (fileSystem.FindFile("engine/widescreen.def") >= 0 && !Args->CheckParm("-nowidescreen"))
 	{
 		loaddefinitionsfile("engine/widescreen.def");
 	}
-
-
+	fileSystem.InitHashChains(); // make sure that any resources that got added can be found again.
 }
 
 bool M_Active()
diff --git a/source/core/gamecontrol.h b/source/core/gamecontrol.h
index 4a3d684b2..d91275260 100644
--- a/source/core/gamecontrol.h
+++ b/source/core/gamecontrol.h
@@ -65,6 +65,7 @@ struct UserConfig
 {
 	FString gamegrp;
 	FString CommandMap;
+	FString UserDef;
 	FString DefaultDef;
 	FString DefaultCon;
 	FString CommandDemo;
diff --git a/source/core/parsefuncs.h b/source/core/parsefuncs.h
index b6f71f8f1..61459d10a 100644
--- a/source/core/parsefuncs.h
+++ b/source/core/parsefuncs.h
@@ -51,6 +51,20 @@ void parseSkip(FScanner& sc, FScriptPosition& pos)
 	for (int i = 0; i < cnt; i++) if (!sc.GetNumber(true)) return;
 }
 
+void parseDefine(FScanner& sc, FScriptPosition& pos)
+{
+	FString name;
+	if (!sc.GetString(name))  return;
+	if (!sc.GetNumber()) return;
+	sc.AddSymbol(name, sc.Number);
+}
+
+//===========================================================================
+//
+//
+//
+//===========================================================================
+
 void parseDefineTexture(FScanner& sc, FScriptPosition& pos)
 {
 	int tile, palette;
@@ -178,3 +192,54 @@ void parseAnimTileRange(FScanner& sc, FScriptPosition& pos)
 	processSetAnim("animtilerange", pos, set);
 }
 
+//===========================================================================
+//
+//
+//
+//===========================================================================
+
+void parseAlphahack(FScanner& sc, FScriptPosition& pos)
+{
+	int tile;
+
+	if (!sc.GetNumber(tile, true)) return;
+	if (!sc.GetFloat(true)) return;
+	if ((unsigned)tile < MAXTILES) TileFiles.tiledata[tile].texture->alphaThreshold = (float)sc.Float;
+}
+
+//===========================================================================
+//
+//
+//
+//===========================================================================
+
+void parseAlphahackRange(FScanner& sc, FScriptPosition& pos)
+{
+	int tilestart, tileend;
+
+	if (!sc.GetNumber(tilestart, true)) return;
+	if (!sc.GetNumber(tileend, true)) return;
+	if (!sc.GetFloat(true)) return;
+	if (!ValidateTileRange("alphahackrange", tilestart, tileend, pos)) return;
+
+	for (int i = tilestart; i <= tileend; i++)
+		TileFiles.tiledata[i].texture->alphaThreshold = (float)sc.Number;
+}
+
+//===========================================================================
+//
+//
+//
+//===========================================================================
+
+void parseDefineTint(FScanner& sc, FScriptPosition& pos)
+{
+	int pal, r, g, b, f;
+
+	if (!sc.GetNumber(pal, true)) return;
+	if (!sc.GetNumber(r)) return;
+	if (!sc.GetNumber(g)) return;
+	if (!sc.GetNumber(b)) return;
+	if (!sc.GetNumber(f)) return;
+	lookups.setPaletteTint(pal, r, g, b, 0, 0, 0, f);
+}
diff --git a/source/games/blood/src/barf.cpp b/source/games/blood/src/barf.cpp
index f5f6f6381..ad218159c 100644
--- a/source/games/blood/src/barf.cpp
+++ b/source/games/blood/src/barf.cpp
@@ -656,7 +656,7 @@ void ParseScript(int lumpnum)
                 if (dword_44CE0[gParseLevel] == 0) 
 				{
 					// In the RFS files I have seen the outermost directory is not part of what goes into the file system.
-					auto inp1 = strchr(inp, '\\');
+					auto inp1 = strpbrk(inp, "/\\");
 					if (!inp1 || !fileSystem.CreatePathlessCopy(inp1 + 1, ID, nFlags))
 					{
 						// I'll activate this when I find evidence that it is needed. Otherwise the risk of picking up unwanted data is too high.
diff --git a/wadsrc/static/filter/exhumed/engine/engine.def b/wadsrc/static/filter/exhumed/engine/engine.def
deleted file mode 100644
index eaa696b26..000000000
--- a/wadsrc/static/filter/exhumed/engine/engine.def
+++ /dev/null
@@ -1 +0,0 @@
-tilefromtexture 3463 { file "tiles/options.png" }
\ No newline at end of file
diff --git a/wadsrc/static/filter/exhumed/tiles/options.png b/wadsrc/static/filter/exhumed/tiles/options.png
deleted file mode 100644
index a035cbae2..000000000
Binary files a/wadsrc/static/filter/exhumed/tiles/options.png and /dev/null differ
diff --git a/wadsrc/static/menudef.txt b/wadsrc/static/menudef.txt
index 675a6b08b..907b26f2d 100644
--- a/wadsrc/static/menudef.txt
+++ b/wadsrc/static/menudef.txt
@@ -1490,6 +1490,14 @@ OptionValue GPUSwitch
 	2.0, "$OPTVAL_INTEGRATED"
 }
 
+OptionValue PreferBackend
+{
+	0, "$OPTVAL_OPENGL"
+	1, "$OPTVAL_VULKAN"
+	// Enable when HAVE_SOFTPOLY will be defined
+	//2, "$OPTVAL_SOFTPOLY"
+}
+
 OptionMenu VideoModeMenu protected
 {
 	Title "$VIDMNU_TITLE"