diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 9815e88e9..4c3ec318b 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -5985,21 +5985,21 @@ doplaysound:			if (funcIndex == ACSF_PlayActorSound)
 		
 		case ACSF_SpawnParticle:
 		{
-			fixed_t x = args[0];
-			fixed_t y = args[1];
-			fixed_t z = args[2];
-			fixed_t xvel = args[3];
-			fixed_t yvel = args[4];
-			fixed_t zvel = args[5];
-			PalEntry color = args[6];
-			int lifetime = args[7];
-			bool fullbright = argCount > 8 ? !!args[8] : false;
-			int startalpha = argCount > 9 ? args[9] : 0xFF; // Byte trans
-			int size = argCount > 10 ? args[10] : 1;
-			int fadestep = argCount > 11 ? args[11] : -1;
-			fixed_t accelx = argCount > 12 ? args[12] : 0;
-			fixed_t accely = argCount > 13 ? args[13] : 0;
-			fixed_t accelz = argCount > 14 ? args[14] : 0;
+			PalEntry color = args[0];
+			bool fullbright = argCount > 1 ? !!args[1] : false;
+			int lifetime = argCount > 2 ? args[2] : 35;
+			int size = argCount > 3 ? args[3] : 1;
+			fixed_t x = argCount > 4 ? args[4] : 0;
+			fixed_t y = argCount > 5 ? args[5] : 0;
+			fixed_t z = argCount > 6 ? args[6] : 0;
+			fixed_t xvel = argCount > 7 ? args[7] : 0;
+			fixed_t yvel = argCount > 8 ? args[8] : 0;
+			fixed_t zvel = argCount > 9 ? args[9] : 0;
+			fixed_t accelx = argCount > 10 ? args[10] : 0;
+			fixed_t accely = argCount > 11 ? args[11] : 0;
+			fixed_t accelz = argCount > 12 ? args[12] : 0;
+			int startalpha = argCount > 13 ? args[13] : 0xFF; // Byte trans			
+			int fadestep = argCount > 14 ? args[14] : -1;
 
 			startalpha = clamp<int>(startalpha, 0, 0xFF); // Clamp to byte
 			lifetime = clamp<int>(lifetime, 0, 0xFF); // Clamp to byte
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 69083d686..963ecbca8 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -1779,7 +1779,8 @@ bool P_SeekerMissile (AActor *actor, angle_t thresh, angle_t turnMax, bool preci
 		angle_t pitch = 0;
 		if (!(actor->flags3 & (MF3_FLOORHUGGER|MF3_CEILINGHUGGER)))
 		{ // Need to seek vertically
-			double dist = MAX(1.0, FVector2(actor->Vec2To(target)).Length());
+			fixedvec2 vec = actor->Vec2To(target);
+			double dist = MAX(1.0, TVector2<double>(vec.x, vec.y).Length());
 			// Aim at a player's eyes and at the middle of the actor for everything else.
 			fixed_t aimheight = target->height/2;
 			if (target->IsKindOf(RUNTIME_CLASS(APlayerPawn)))
@@ -2516,7 +2517,7 @@ void P_ZMovement (AActor *mo, fixed_t oldfloorz)
 		{
 			if ((mo->flags & MF_MISSILE) && !(mo->flags & MF_NOCLIP))
 			{
-				mo->AddZ(mo->floorz);
+				mo->SetZ(mo->floorz);
 				if (mo->BounceFlags & BOUNCE_Floors)
 				{
 					mo->FloorBounceMissile (mo->floorsector->floorplane);
@@ -3342,7 +3343,7 @@ void AActor::Tick ()
 
 		UnlinkFromWorld ();
 		flags |= MF_NOBLOCKMAP;
-		SetXYZ(Vec3Offset(velx, vely, vely));
+		SetXYZ(Vec3Offset(velx, vely, velz));
 		SetMovement(velx, vely, velz);
 		LinkToWorld ();
 	}
diff --git a/src/p_spec.cpp b/src/p_spec.cpp
index bcab07508..f40f6c8ef 100644
--- a/src/p_spec.cpp
+++ b/src/p_spec.cpp
@@ -463,7 +463,7 @@ void P_PlayerInSpecialSector (player_t *player, sector_t * sector)
 			}
 			else if (level.time % sector->damageinterval == 0)
 			{
-				P_DamageMobj(player->mo, NULL, NULL, sector->damageamount, sector->damagetype);
+				if (!(player->cheats & (CF_GODMODE|CF_GODMODE2))) P_DamageMobj(player->mo, NULL, NULL, sector->damageamount, sector->damagetype);
 				if ((sector->Flags & SECF_ENDLEVEL) && player->health <= 10 && (!deathmatch || !(dmflags & DF_NO_EXIT)))
 				{
 					G_ExitLevel(0, false);
diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index 6a03a727f..5054d8fe5 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -2882,34 +2882,66 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_SpawnDebris)
 // A_SpawnParticle
 //
 //===========================================================================
+enum SPFflag
+{
+	SPF_FULLBRIGHT =		1,
+	SPF_RELPOS =			1 << 1,
+	SPF_RELVEL =			1 << 2,
+	SPF_RELACCEL =			1 << 3,
+	SPF_RELANG =			1 << 4,
+};
+
 DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_SpawnParticle)
 {
 	PARAM_ACTION_PROLOGUE;
-	PARAM_FIXED		(xoff);
-	PARAM_FIXED		(yoff);
-	PARAM_FIXED		(zoff);
-	PARAM_FIXED		(xvel);
-	PARAM_FIXED		(yvel);
-	PARAM_FIXED		(zvel);
 	PARAM_COLOR		(color);
-	PARAM_INT		(lifetime);
-	PARAM_BOOL_OPT	(fullbright)	{ fullbright = false; }
-	PARAM_INT_OPT	(startalpha)	{ startalpha = 255; }	// Byte trans
-	PARAM_INT_OPT	(size)			{ size = -1; }
-	PARAM_INT_OPT	(fadestep)		{ fadestep = -1; }
+	PARAM_INT_OPT	(flags)			{ flags = 0; }
+	PARAM_INT_OPT	(lifetime)		{ lifetime = 35; }
+	PARAM_INT_OPT	(size)			{ size = 1; }
+	PARAM_ANGLE_OPT	(angle)			{ angle = 0; }
+	PARAM_FIXED_OPT	(xoff)			{ xoff = 0; }
+	PARAM_FIXED_OPT	(yoff)			{ yoff = 0; }
+	PARAM_FIXED_OPT	(zoff)			{ zoff = 0; }
+	PARAM_FIXED_OPT	(xvel)			{ xvel = 0; }
+	PARAM_FIXED_OPT	(yvel)			{ yvel = 0; }
+	PARAM_FIXED_OPT	(zvel)			{ zvel = 0; }
 	PARAM_FIXED_OPT	(accelx)		{ accelx = 0; }
 	PARAM_FIXED_OPT	(accely)		{ accely = 0; }
 	PARAM_FIXED_OPT	(accelz)		{ accelz = 0; }
+	PARAM_FIXED_OPT	(startalphaf)	{ startalphaf = FRACUNIT; }
+	PARAM_FIXED_OPT	(fadestepf)		{ fadestepf = -FRACUNIT; }
 
-	startalpha = clamp<int>(startalpha, 0, 0xFF); // Clamp to byte
-	lifetime = clamp<int>(lifetime, 0, 0xFF); // Clamp to byte
-	fadestep = clamp<int>(fadestep, -1, 0xFF); // Clamp to byte inc. -1 (indicating automatic)
+	BYTE startalpha = (BYTE)(clamp(startalphaf, 0, FRACUNIT) * 255 / FRACUNIT);
+	int fadestep = fadestepf < 0 ? -1 : clamp(fadestepf, 0, FRACUNIT) * 255 / FRACUNIT;
 	size = clamp<int>(size, 0, 0xFF); // Clamp to byte
 
 	if (lifetime != 0)
 	{
-		fixedvec3 pos = self->Vec3Offset(xoff, yoff, zoff);
-		P_SpawnParticle(pos.x, pos.y, pos.z, xvel, yvel, zvel, color, fullbright, startalpha, lifetime, size, fadestep, accelx, accely, accelz);
+		const angle_t ang = (angle + ((flags & SPF_RELANG) ? self->angle : 0)) >> ANGLETOFINESHIFT;
+		fixedvec3 pos;
+		//[MC] Code ripped right out of A_SpawnItemEx.
+		if (flags & SPF_RELPOS)
+		{
+			// in relative mode negative y values mean 'left' and positive ones mean 'right'
+			// This is the inverse orientation of the absolute mode!
+			const fixed_t xof1 = xoff;
+			xoff = FixedMul(xof1, finecosine[ang]) + FixedMul(yoff, finesine[ang]);
+			yoff = FixedMul(xof1, finesine[ang]) - FixedMul(yoff, finecosine[ang]);
+		}
+		if (flags & SPF_RELVEL)
+		{
+			const fixed_t newxvel = FixedMul(xvel, finecosine[ang]) + FixedMul(yvel, finesine[ang]);
+			yvel = FixedMul(xvel, finesine[ang]) - FixedMul(yvel, finecosine[ang]);
+			xvel = newxvel;
+		}
+		if (flags & SPF_RELACCEL)
+		{
+			fixed_t newaccelx = FixedMul(accelx, finecosine[ang]) + FixedMul(accely, finesine[ang]);
+			accely = FixedMul(accelx, finesine[ang]) - FixedMul(accely, finecosine[ang]);
+			accelx = newaccelx;
+		}
+		pos = self->Vec3Offset(xoff, yoff, zoff);
+		P_SpawnParticle(pos.x, pos.y, pos.z, xvel, yvel, zvel, color, !!(flags & SPF_FULLBRIGHT), startalpha, lifetime, size, fadestep, accelx, accely, accelz);
 	}
 	return 0;
 }
@@ -6438,4 +6470,4 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_CheckBlock)
 		ACTION_JUMP(block);
 	}
 	return numret;
-}
+}
diff --git a/wadsrc/static/actors/actor.txt b/wadsrc/static/actors/actor.txt
index 82b861b48..40c7b4288 100644
--- a/wadsrc/static/actors/actor.txt
+++ b/wadsrc/static/actors/actor.txt
@@ -202,7 +202,7 @@ ACTOR Actor native //: Thinker
 	action native A_SetScale(float scalex, float scaley = 0, int ptr = AAPTR_DEFAULT);
 	action native A_SetMass(int mass);
 	action native A_SpawnDebris(class<Actor> spawntype, bool transfer_translation = false, float mult_h = 1, float mult_v = 1);
-	action native A_SpawnParticle(float xoff, float yoff, float zoff, float velx, float vely, float velz, color color1, int lifetime, bool fullbright = false, int startalpha = 255, int size = 1, int fadestep = -1, float accelx = 0.0, float accely = 0.0, float accelz = 0.0);
+	action native A_SpawnParticle(color color1, int flags = 0, int lifetime = 35, int size = 1, float angle = 0, float xoff = 0, float yoff = 0, float zoff = 0, float velx = 0, float vely = 0, float velz = 0, float accelx = 0, float accely = 0, float accelz = 0, float startalphaf = 1, float fadestepf = -1);
 	action native A_CheckSight(state label);
 	action native A_ExtChase(bool usemelee, bool usemissile, bool playactive = true, bool nightmarefast = false);
 	action native A_DropInventory(class<Inventory> itemtype);
diff --git a/wadsrc/static/actors/constants.txt b/wadsrc/static/actors/constants.txt
index f750772b1..51e8e845d 100644
--- a/wadsrc/static/actors/constants.txt
+++ b/wadsrc/static/actors/constants.txt
@@ -510,3 +510,14 @@ enum
 	CBF_SETTRACER		= 1 << 3,	//^ but with tracer.
 	CBF_SETONPTR		= 1 << 4,	//Sets the pointer change on the actor doing the checking instead of self.
 };
+
+enum
+{
+	SPF_FULLBRIGHT =	1,
+	SPF_RELPOS =		1 << 1,
+	SPF_RELVEL =		1 << 2,
+	SPF_RELACCEL =		1 << 3,
+	SPF_RELANG =		1 << 4,
+
+	SPF_RELATIVE =	SPF_RELPOS|SPF_RELVEL|SPF_RELACCEL|SPF_RELANG
+};