diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b7f85541c..950cfe9c0 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1232,6 +1232,7 @@ set (PCH_SOURCES
 	scripting/thingdef_data.cpp
 	scripting/thingdef_properties.cpp
 	scripting/backend/codegen.cpp
+	scripting/backend/scopebarrier.cpp
 	scripting/backend/dynarrays.cpp
 	scripting/backend/vmbuilder.cpp
 	scripting/backend/vmdisasm.cpp
diff --git a/src/dobject.h b/src/dobject.h
index d99fbee2b..cc6672cdf 100644
--- a/src/dobject.h
+++ b/src/dobject.h
@@ -207,7 +207,9 @@ enum EObjectFlags
 	OF_Transient		= 1 << 11,		// Object should not be archived (references to it will be nulled on disk)
 	OF_Spawned			= 1 << 12,      // Thinker was spawned at all (some thinkers get deleted before spawning)
 	OF_Released			= 1 << 13,		// Object was released from the GC system and should not be processed by GC function
-	OF_Abstract			= 1 << 14,		// Marks a class that cannot be created with CreateNew
+	OF_Abstract			= 1 << 14,		// Marks a class that cannot be created with new() function at all
+	OF_UI				= 1 << 15,		// Marks a class that defaults to VARF_UI for it's fields/methods
+	OF_Play				= 1 << 16,		// Marks a class that defaults to VARF_Play for it's fields/methods
 };
 
 template<class T> class TObjPtr;
diff --git a/src/dobjtype.h b/src/dobjtype.h
index 1a30b42ed..1d134bd07 100644
--- a/src/dobjtype.h
+++ b/src/dobjtype.h
@@ -37,6 +37,10 @@ enum
 	VARF_Transient		= (1<<17),  // don't auto serialize field.
 	VARF_Meta			= (1<<18),	// static class data (by necessity read only.)
 	VARF_VarArg			= (1<<19),  // [ZZ] vararg: don't typecheck values after ... in function signature
+	VARF_UI				= (1<<20),  // [ZZ] ui: object is ui-scope only (can't modify playsim)
+	VARF_Play			= (1<<21),  // [ZZ] play: object is playsim-scope only (can't access ui)
+	VARF_VirtualScope	= (1<<22),  // [ZZ] virtualscope: object should use the scope of the particular class it's being used with (methods only)
+	VARF_ClearScope		= (1<<23),  // [ZZ] clearscope: this method ignores the member access chain that leads to it and is always plain data.
 };
 
 // An action function -------------------------------------------------------
diff --git a/src/events.cpp b/src/events.cpp
index a0780fb92..9946a1059 100755
--- a/src/events.cpp
+++ b/src/events.cpp
@@ -117,6 +117,21 @@ bool E_UnregisterHandler(DStaticEventHandler* handler)
 	return true;
 }
 
+bool E_SendNetworkEvent(FString name, int arg1, int arg2, int arg3)
+{
+	if (gamestate != GS_LEVEL)
+		return false;
+
+	Net_WriteByte(DEM_NETEVENT);
+	Net_WriteString(name);
+	Net_WriteByte(3);
+	Net_WriteLong(arg1);
+	Net_WriteLong(arg2);
+	Net_WriteLong(arg3);
+
+	return true;
+}
+
 bool E_CheckHandler(DStaticEventHandler* handler)
 {
 	for (DStaticEventHandler* lhandler = E_FirstEventHandler; lhandler; lhandler = lhandler->next)
@@ -521,6 +536,18 @@ DEFINE_ACTION_FUNCTION(DStaticEventHandler, SetOrder)
 	return 0;
 }
 
+DEFINE_ACTION_FUNCTION(DEventHandler, SendNetworkEvent)
+{
+	PARAM_PROLOGUE;
+	PARAM_STRING(name);
+	PARAM_INT(arg1);
+	PARAM_INT(arg2);
+	PARAM_INT(arg3);
+	//
+
+	ACTION_RETURN_BOOL(E_SendNetworkEvent(name, arg1, arg2, arg3));
+}
+
 DEFINE_ACTION_FUNCTION(DEventHandler, Create)
 {
 	PARAM_PROLOGUE;
@@ -658,6 +685,7 @@ DEFINE_EMPTY_HANDLER(DStaticEventHandler, UiProcess);
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, InputProcess);
 
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, ConsoleProcess);
+DEFINE_EMPTY_HANDLER(DStaticEventHandler, NetworkProcess);
 
 // ===========================================
 //
@@ -1068,22 +1096,45 @@ static DConsoleEvent* E_SetupConsoleEvent()
 
 void DStaticEventHandler::ConsoleProcess(int player, FString name, int arg1, int arg2, int arg3)
 {
-	IFVIRTUAL(DStaticEventHandler, ConsoleProcess)
+	if (player < 0)
 	{
-		// don't create excessive DObjects if not going to be processed anyway
-		if (func == DStaticEventHandler_ConsoleProcess_VMPtr)
-			return;
-		DConsoleEvent* e = E_SetupConsoleEvent();
+		IFVIRTUAL(DStaticEventHandler, ConsoleProcess)
+		{
+			// don't create excessive DObjects if not going to be processed anyway
+			if (func == DStaticEventHandler_ConsoleProcess_VMPtr)
+				return;
+			DConsoleEvent* e = E_SetupConsoleEvent();
 
-		//
-		e->Player = player;
-		e->Name = name;
-		e->Args[0] = arg1;
-		e->Args[1] = arg2;
-		e->Args[2] = arg3;
+			//
+			e->Player = player;
+			e->Name = name;
+			e->Args[0] = arg1;
+			e->Args[1] = arg2;
+			e->Args[2] = arg3;
 
-		VMValue params[2] = { (DStaticEventHandler*)this, e };
-		GlobalVMStack.Call(func, params, 2, nullptr, 0, nullptr);
+			VMValue params[2] = { (DStaticEventHandler*)this, e };
+			GlobalVMStack.Call(func, params, 2, nullptr, 0, nullptr);
+		}
+	}
+	else
+	{
+		IFVIRTUAL(DStaticEventHandler, NetworkProcess)
+		{
+			// don't create excessive DObjects if not going to be processed anyway
+			if (func == DStaticEventHandler_NetworkProcess_VMPtr)
+				return;
+			DConsoleEvent* e = E_SetupConsoleEvent();
+
+			//
+			e->Player = player;
+			e->Name = name;
+			e->Args[0] = arg1;
+			e->Args[1] = arg2;
+			e->Args[2] = arg3;
+
+			VMValue params[2] = { (DStaticEventHandler*)this, e };
+			GlobalVMStack.Call(func, params, 2, nullptr, 0, nullptr);
+		}
 	}
 }
 
@@ -1136,10 +1187,6 @@ CCMD(netevent)
 		for (int i = 0; i < argn; i++)
 			arg[i] = atoi(argv[2 + i]);
 		// call networked
-		Net_WriteByte(DEM_NETEVENT);
-		Net_WriteString(argv[1]);
-		Net_WriteByte(argn);
-		for (int i = 0; i < 3; i++)
-			Net_WriteLong(arg[i]);
+		E_SendNetworkEvent(argv[1], arg[0], arg[1], arg[2]);
 	}
 }
diff --git a/src/events.h b/src/events.h
index fa63e7325..b83890223 100755
--- a/src/events.h
+++ b/src/events.h
@@ -60,6 +60,9 @@ bool E_Responder(event_t* ev); // splits events into InputProcess and UiProcess
 // this executes on console/net events.
 void E_Console(int player, FString name, int arg1, int arg2, int arg3);
 
+// send networked event. unified function.
+bool E_SendNetworkEvent(FString name, int arg1, int arg2, int arg3);
+
 // check if there is anything that should receive GUI events
 bool E_CheckUiProcessors();
 // check if we need native mouse due to UiProcessors
diff --git a/src/menu/menu.cpp b/src/menu/menu.cpp
index 1c8e0b39b..a481dd24b 100644
--- a/src/menu/menu.cpp
+++ b/src/menu/menu.cpp
@@ -796,7 +796,16 @@ void M_ClearMenus()
 
 void M_Init (void) 
 {
-	M_ParseMenuDefs();
+	try
+	{
+		M_ParseMenuDefs();
+	}
+	catch (CVMAbortException &err)
+	{
+		err.MaybePrintMessage();
+		Printf("%s", err.stacktrace.GetChars());
+		I_FatalError("Failed to initialize menus");
+	}
 	M_CreateMenus();
 }
 
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 027b614ea..8c2859479 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -4765,24 +4765,24 @@ static int ScriptCall(unsigned argc, int32_t *args)
 		auto cls = PClass::FindClass(clsname);
 		if (!cls)
 		{
-			I_Error("ACS call to unknown class in script function %s.%s", cls, funcname);
+			I_Error("ACS call to unknown class in script function %s.%s", clsname, funcname);
 		}
 		auto funcsym = dyn_cast<PFunction>(cls->Symbols.FindSymbol(funcname, true));
 		if (funcsym == nullptr)
 		{
-			I_Error("ACS call to unknown script function %s.%s", cls, funcname);
+			I_Error("ACS call to unknown script function %s.%s", clsname, funcname);
 		}
 		auto func = funcsym->Variants[0].Implementation;
 		if (func->ImplicitArgs > 0)
 		{
-			I_Error("ACS call to non-static script function %s.%s", cls, funcname);
+			I_Error("ACS call to non-static script function %s.%s", clsname, funcname);
 		}
 		TArray<VMValue> params;
 		for (unsigned i = 2; i < argc; i++)
 		{
 			if (func->Proto->ArgumentTypes.Size() < i - 1)
 			{
-				I_Error("Too many parameters in call to %s.%s", cls, funcname);
+				I_Error("Too many parameters in call to %s.%s", clsname, funcname);
 			}
 			auto argtype = func->Proto->ArgumentTypes[i - 2];
 			// The only types allowed are int, bool, double, Name, Sound, Color and String
@@ -4812,7 +4812,7 @@ static int ScriptCall(unsigned argc, int32_t *args)
 			}
 			else
 			{
-				I_Error("Invalid type %s in call to %s.%s", argtype->DescriptiveName(), cls, funcname);
+				I_Error("Invalid type %s in call to %s.%s", argtype->DescriptiveName(), clsname, funcname);
 			}
 		}
 		if (func->Proto->ArgumentTypes.Size() > params.Size())
@@ -4820,7 +4820,7 @@ static int ScriptCall(unsigned argc, int32_t *args)
 			// Check if we got enough parameters. That means we either cover the full argument list of the function or the next argument is optional.
 			if (!(funcsym->Variants[0].ArgFlags[params.Size()] & VARF_Optional))
 			{
-				I_Error("Insufficient parameters in call to %s.%s", cls, funcname);
+				I_Error("Insufficient parameters in call to %s.%s", clsname, funcname);
 			}
 		}
 		// The return value can be the same types as the parameter types, plus void
diff --git a/src/sc_man_scanner.re b/src/sc_man_scanner.re
index d4a1254d6..ba839813f 100644
--- a/src/sc_man_scanner.re
+++ b/src/sc_man_scanner.re
@@ -170,6 +170,10 @@ std2:
 		'virtual'					{ RET(TK_Virtual); }
 		'override'					{ RET(TK_Override); }
 		'vararg'					{ RET(TK_VarArg); }
+		'ui'						{ RET(TK_UI); }
+		'play'						{ RET(TK_Play); }
+		'clearscope'				{ RET(TK_ClearScope); }
+		'virtualscope'				{ RET(TK_VirtualScope); }
 		'super'						{ RET(TK_Super); }
 		'global'					{ RET(TK_Global); }
 		'stop'						{ RET(TK_Stop); }
diff --git a/src/sc_man_tokens.h b/src/sc_man_tokens.h
index 0227dffa9..320601414 100644
--- a/src/sc_man_tokens.h
+++ b/src/sc_man_tokens.h
@@ -112,6 +112,10 @@ xx(TK_Optional,				"'optional'")
 xx(TK_Export,				"'expert'")
 xx(TK_Virtual,				"'virtual'")
 xx(TK_VarArg,               "'vararg'")
+xx(TK_UI,					"'ui'")
+xx(TK_Play,					"'play'")
+xx(TK_ClearScope,			"'clearscope'")
+xx(TK_VirtualScope,			"'virtualscope'")
 xx(TK_Override,				"'override'")
 xx(TK_Super,				"'super'")
 xx(TK_Null,					"'null'")
diff --git a/src/scripting/backend/codegen.cpp b/src/scripting/backend/codegen.cpp
index 8e41f44ab..eb92fe974 100644
--- a/src/scripting/backend/codegen.cpp
+++ b/src/scripting/backend/codegen.cpp
@@ -89,6 +89,37 @@ static const FLOP FxFlops[] =
 	{ NAME_TanH,	FLOP_TANH,		[](double v) { return g_tanh(v); } },
 };
 
+
+//==========================================================================
+//
+// [ZZ] Magic methods to be used in vmexec.h for runtime checking of scope
+//
+//==========================================================================
+
+// this can be imported in vmexec.h
+void FScopeBarrier_ValidateNew(PClass* cls, PFunction* callingfunc)
+{
+	int outerside = callingfunc->Variants.Size() ? FScopeBarrier::SideFromFlags(callingfunc->Variants[0].Flags) : FScopeBarrier::Side_Virtual;
+	if (outerside == FScopeBarrier::Side_Virtual)
+		outerside = FScopeBarrier::SideFromObjectFlags(callingfunc->OwningClass->ObjectFlags);
+	int innerside = FScopeBarrier::SideFromObjectFlags(cls->ObjectFlags);
+	if ((outerside != innerside) && (innerside != FScopeBarrier::Side_PlainData)) // "cannot construct ui class ... from data context"
+		ThrowAbortException(X_OTHER, "Cannot construct %s class %s from %s context", FScopeBarrier::StringFromSide(innerside), cls->TypeName.GetChars(), FScopeBarrier::StringFromSide(outerside));
+}
+// this can be imported in vmexec.h
+void FScopeBarrier_ValidateCall(PFunction* calledfunc, PFunction* callingfunc, PClass* selftype)
+{
+	// [ZZ] anonymous blocks have 0 variants, so give them Side_Virtual.
+	int outerside = callingfunc->Variants.Size() ? FScopeBarrier::SideFromFlags(callingfunc->Variants[0].Flags) : FScopeBarrier::Side_Virtual;
+	if (outerside == FScopeBarrier::Side_Virtual)
+		outerside = FScopeBarrier::SideFromObjectFlags(callingfunc->OwningClass->ObjectFlags);
+	int innerside = FScopeBarrier::SideFromFlags(calledfunc->Variants[0].Flags);
+	if (innerside == FScopeBarrier::Side_Virtual)
+		innerside = FScopeBarrier::SideFromObjectFlags(selftype->ObjectFlags);
+	if ((outerside != innerside) && (innerside != FScopeBarrier::Side_PlainData))
+		ThrowAbortException(X_OTHER, "Cannot call %s function %s from %s context", FScopeBarrier::StringFromSide(innerside), calledfunc->SymbolName.GetChars(), FScopeBarrier::StringFromSide(outerside));
+}
+
 //==========================================================================
 //
 // FCompileContext
@@ -167,7 +198,8 @@ void FCompileContext::CheckReturn(PPrototype *proto, FScriptPosition &pos)
 	}
 }
 
-bool FCompileContext::CheckReadOnly(int flags)
+// [ZZ] I find it really dumb that something called CheckReadOnly returns false for readonly. renamed.
+bool FCompileContext::CheckWritable(int flags)
 {
 	if (!(flags & VARF_ReadOnly)) return false;
 	if (!(flags & VARF_InternalAccess)) return true;
@@ -5023,6 +5055,7 @@ FxNew::FxNew(FxExpression *v)
 {
 	val = new FxClassTypeCast(NewClassPointer(RUNTIME_CLASS(DObject)), v, false);
 	ValueType = NewPointer(RUNTIME_CLASS(DObject));
+	CallingFunction = nullptr;
 }
 
 //==========================================================================
@@ -5047,6 +5080,7 @@ FxExpression *FxNew::Resolve(FCompileContext &ctx)
 	CHECKRESOLVED();
 	SAFE_RESOLVE(val, ctx);
 
+	CallingFunction = ctx.Function;
 	if (!val->ValueType->IsKindOf(RUNTIME_CLASS(PClassPointer)))
 	{
 		ScriptPosition.Message(MSG_ERROR, "Class type expected");
@@ -5056,8 +5090,28 @@ FxExpression *FxNew::Resolve(FCompileContext &ctx)
 	if (val->isConstant())
 	{
 		auto cls = static_cast<PClass *>(static_cast<FxConstant*>(val)->GetValue().GetPointer());
+		if (cls->ObjectFlags & OF_Abstract)
+		{
+			ScriptPosition.Message(MSG_ERROR, "Cannot instantiate abstract class %s", cls->TypeName.GetChars());
+			delete this;
+			return nullptr;
+		}
+
+		//
+		int outerside = ctx.Function && ctx.Function->Variants.Size() ? FScopeBarrier::SideFromFlags(ctx.Function->Variants[0].Flags) : FScopeBarrier::Side_Virtual;
+		if (outerside == FScopeBarrier::Side_Virtual)
+			outerside = FScopeBarrier::SideFromObjectFlags(ctx.Class->ObjectFlags);
+		int innerside = FScopeBarrier::SideFromObjectFlags(cls->ObjectFlags);
+		if ((outerside != innerside) && (innerside != FScopeBarrier::Side_PlainData)) // "cannot construct ui class ... from data context"
+		{
+			ScriptPosition.Message(MSG_ERROR, "Cannot construct %s class %s from %s context", FScopeBarrier::StringFromSide(innerside), cls->TypeName.GetChars(), FScopeBarrier::StringFromSide(outerside));
+			delete this;
+			return nullptr;
+		}
+
 		ValueType = NewPointer(cls);
 	}
+
 	return this;
 }
 
@@ -5072,7 +5126,7 @@ ExpEmit FxNew::Emit(VMFunctionBuilder *build)
 	ExpEmit from = val->Emit(build);
 	from.Free(build);
 	ExpEmit to(build, REGT_POINTER);
-	build->Emit(from.Konst ? OP_NEW_K : OP_NEW, to.RegNum, from.RegNum);
+	build->Emit(from.Konst ? OP_NEW_K : OP_NEW, to.RegNum, from.RegNum, build->GetConstantAddress(CallingFunction, ATAG_OBJECT));
 	return to;
 }
 
@@ -6245,7 +6299,7 @@ FxExpression *FxLocalVariable::Resolve(FCompileContext &ctx)
 bool FxLocalVariable::RequestAddress(FCompileContext &ctx, bool *writable)
 {
 	AddressRequested = true;
-	if (writable != nullptr) *writable = !ctx.CheckReadOnly(Variable->VarFlags);
+	if (writable != nullptr) *writable = !ctx.CheckWritable(Variable->VarFlags);
 	return true;
 }
 	
@@ -6463,7 +6517,7 @@ FxGlobalVariable::FxGlobalVariable(PField* mem, const FScriptPosition &pos)
 bool FxGlobalVariable::RequestAddress(FCompileContext &ctx, bool *writable)
 {
 	AddressRequested = true;
-	if (writable != nullptr) *writable = AddressWritable && !ctx.CheckReadOnly(membervar->Flags);
+	if (writable != nullptr) *writable = AddressWritable && !ctx.CheckWritable(membervar->Flags);
 	return true;
 }
 
@@ -6653,7 +6707,7 @@ FxStackVariable::~FxStackVariable()
 bool FxStackVariable::RequestAddress(FCompileContext &ctx, bool *writable)
 {
 	AddressRequested = true;
-	if (writable != nullptr) *writable = AddressWritable && !ctx.CheckReadOnly(membervar->Flags);
+	if (writable != nullptr) *writable = AddressWritable && !ctx.CheckWritable(membervar->Flags);
 	return true;
 }
 
@@ -6751,8 +6805,34 @@ bool FxStructMember::RequestAddress(FCompileContext &ctx, bool *writable)
 		return false;
 	}
 	AddressRequested = true;
-	if (writable != nullptr) *writable = (AddressWritable && !ctx.CheckReadOnly(membervar->Flags) &&
-											(!classx->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)) || !static_cast<PPointer*>(classx->ValueType)->IsConst));
+	if (writable != nullptr)
+	{
+		// [ZZ] original check.
+		bool bWritable = (AddressWritable && !ctx.CheckWritable(membervar->Flags) &&
+			(!classx->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)) || !static_cast<PPointer*>(classx->ValueType)->IsConst));
+		// [ZZ] self in a const function is not writable.
+		if (bWritable) // don't do complex checks on early fail
+		{
+			if ((classx->ExprType == EFX_Self) && (ctx.Function && (ctx.Function->Variants[0].Flags & VARF_ReadOnly)))
+				bWritable = false;
+		}
+		// [ZZ] implement write barrier between different scopes
+		if (bWritable)
+		{
+			int outerflags = 0;
+			if (ctx.Function)
+			{
+				outerflags = ctx.Function->Variants[0].Flags;
+				if (((outerflags & (VARF_VirtualScope | VARF_Virtual)) == (VARF_VirtualScope | VARF_Virtual)) && ctx.Class)
+					outerflags = FScopeBarrier::FlagsFromSide(FScopeBarrier::SideFromObjectFlags(ctx.Class->ObjectFlags));
+			}
+			FScopeBarrier scopeBarrier(outerflags, FScopeBarrier::FlagsFromSide(BarrierSide), membervar->SymbolName.GetChars());
+			if (!scopeBarrier.writable)
+				bWritable = false;
+		}
+
+		*writable = bWritable;
+	}
 	return true;
 }
 
@@ -6772,7 +6852,7 @@ FxExpression *FxStructMember::Resolve(FCompileContext &ctx)
 		if (!classx->ValueType->IsKindOf(RUNTIME_CLASS(PPointer))
 			|| !static_cast<PPointer *>(classx->ValueType)->PointedType->IsKindOf(RUNTIME_CLASS(AActor)))
 		{
-			ScriptPosition.Message(MSG_ERROR, "'Default' requires an actor type.");
+			ScriptPosition.Message(MSG_ERROR, "'Default' requires an actor type");
 			delete this;
 			return nullptr;
 		}
@@ -6782,12 +6862,36 @@ FxExpression *FxStructMember::Resolve(FCompileContext &ctx)
 		return x->Resolve(ctx);
 	}
 
+	// [ZZ] support magic
+	int outerflags = 0;
+	if (ctx.Function)
+	{
+		outerflags = ctx.Function->Variants[0].Flags;
+		if (((outerflags & (VARF_VirtualScope | VARF_Virtual)) == (VARF_VirtualScope | VARF_Virtual)) && ctx.Class)
+			outerflags = FScopeBarrier::FlagsFromSide(FScopeBarrier::SideFromObjectFlags(ctx.Class->ObjectFlags));
+	}
+	FScopeBarrier scopeBarrier(outerflags, membervar->Flags, membervar->SymbolName.GetChars());
+	if (!scopeBarrier.readable)
+	{
+		ScriptPosition.Message(MSG_ERROR, "%s", scopeBarrier.readerror.GetChars());
+		delete this;
+		return nullptr;
+	}
+
+	BarrierSide = scopeBarrier.sidelast;
+	if (classx->ExprType == EFX_StructMember && ExprType == EFX_StructMember) // note: only do this for structs now
+	{
+		FxStructMember* pmember = (FxStructMember*)classx;
+		if (BarrierSide == FScopeBarrier::Side_PlainData && pmember)
+			BarrierSide = pmember->BarrierSide;
+	}
+
 	if (classx->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)))
 	{
 		PPointer *ptrtype = dyn_cast<PPointer>(classx->ValueType);
 		if (ptrtype == nullptr || !ptrtype->PointedType->IsKindOf(RUNTIME_CLASS(PStruct)))
 		{
-			ScriptPosition.Message(MSG_ERROR, "Member variable requires a struct or class object.");
+			ScriptPosition.Message(MSG_ERROR, "Member variable requires a struct or class object");
 			delete this;
 			return nullptr;
 		}
@@ -6799,7 +6903,8 @@ FxExpression *FxStructMember::Resolve(FCompileContext &ctx)
 		{
 			auto parentfield = static_cast<FxMemberBase *>(classx)->membervar;
 			// PFields are garbage collected so this will be automatically taken care of later.
-			auto newfield = new PField(NAME_None, membervar->Type, membervar->Flags | parentfield->Flags, membervar->Offset + parentfield->Offset);
+			// [ZZ] call ChangeSideInFlags to ensure that we don't get ui+play
+			auto newfield = new PField(NAME_None, membervar->Type, FScopeBarrier::ChangeSideInFlags(membervar->Flags | parentfield->Flags, BarrierSide), membervar->Offset + parentfield->Offset);
 			newfield->BitValue = membervar->BitValue;
 			static_cast<FxMemberBase *>(classx)->membervar = newfield;
 			classx->isresolved = false;	// re-resolve the parent so it can also check if it can be optimized away.
@@ -6841,7 +6946,7 @@ FxExpression *FxStructMember::Resolve(FCompileContext &ctx)
 		{
 			if (!(classx->RequestAddress(ctx, &AddressWritable)))
 			{
-				ScriptPosition.Message(MSG_ERROR, "unable to dereference left side of %s", membervar->SymbolName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Unable to dereference left side of %s", membervar->SymbolName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -7371,6 +7476,32 @@ FxExpression *FxFunctionCall::Resolve(FCompileContext& ctx)
 				return nullptr;
 			}
 
+			// [ZZ] validate call
+			PClass* cls = (PClass*)ctx.Class;
+			int outerflags = 0;
+			if (ctx.Function)
+			{
+				outerflags = ctx.Function->Variants[0].Flags;
+				if (((outerflags & (VARF_VirtualScope | VARF_Virtual)) == (VARF_VirtualScope | VARF_Virtual)) && ctx.Class)
+					outerflags = FScopeBarrier::FlagsFromSide(FScopeBarrier::SideFromObjectFlags(ctx.Class->ObjectFlags));
+			}
+			int innerflags = afd->Variants[0].Flags;
+			int innerside = FScopeBarrier::SideFromFlags(innerflags);
+			// [ZZ] check this at compile time. this would work for most legit cases.
+			if (innerside == FScopeBarrier::Side_Virtual)
+			{
+				innerside = FScopeBarrier::SideFromObjectFlags(cls->ObjectFlags);
+				innerflags = FScopeBarrier::FlagsFromSide(innerside);
+			}
+			FScopeBarrier scopeBarrier(outerflags, innerflags, MethodName.GetChars());
+			if (!scopeBarrier.callable)
+			{
+				ScriptPosition.Message(MSG_ERROR, "%s", scopeBarrier.callerror.GetChars());
+				delete this;
+				return nullptr;
+			}
+
+			// [ZZ] this is only checked for VARF_Methods in the other place. bug?
 			if (!CheckFunctionCompatiblity(ScriptPosition, ctx.Function, afd))
 			{
 				delete this;
@@ -7593,8 +7724,18 @@ FxExpression *FxFunctionCall::Resolve(FCompileContext& ctx)
 		break;
 
 	case NAME_New:
-		if (CheckArgSize(MethodName, ArgList, 1, 1, ScriptPosition))
+		if (CheckArgSize(MethodName, ArgList, 0, 1, ScriptPosition))
 		{
+			// [ZZ] allow implicit new() call to mean "create current class instance"
+			if (!ArgList.Size() && !ctx.Class->IsKindOf(RUNTIME_CLASS(PClass)))
+			{
+				ScriptPosition.Message(MSG_ERROR, "Cannot use implicit new() in a struct");
+				delete this;
+				return nullptr;
+			}
+			else if (!ArgList.Size())
+				ArgList.Push(new FxConstant((PClass*)ctx.Class, NewClassPointer((PClass*)ctx.Class), ScriptPosition));
+
 			func = new FxNew(ArgList[0]);
 			ArgList[0] = nullptr;
 		}
@@ -7651,13 +7792,14 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 	PStruct *cls;
 	bool staticonly = false;
 	bool novirtual = false;
+	bool isreadonly = false;
 
 	PStruct *ccls = nullptr;
 
 	if (ctx.Class == nullptr)
 	{
 		// There's no way that a member function call can resolve to a constant so abort right away.
-		ScriptPosition.Message(MSG_ERROR, "Expression is not constant.");
+		ScriptPosition.Message(MSG_ERROR, "Expression is not constant");
 		delete this;
 		return nullptr;
 	}
@@ -7666,7 +7808,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 	{
 		if (a == nullptr)
 		{
-			ScriptPosition.Message(MSG_ERROR, "Empty function argument.");
+			ScriptPosition.Message(MSG_ERROR, "Empty function argument");
 			delete this;
 			return nullptr;
 		}
@@ -7677,6 +7819,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		auto id = static_cast<FxIdentifier *>(Self)->Identifier;
 		// If the left side is a class name for a static member function call it needs to be resolved manually 
 		// because the resulting value type would cause problems in nearly every other place where identifiers are being used.
+		// [ZZ] substitute ccls for String internal type.
 		if (id == NAME_String) ccls = TypeStringStruct;
 		else ccls = FindStructType(id, ctx);
 		if (ccls != nullptr) static_cast<FxIdentifier *>(Self)->noglobal = true;
@@ -7688,7 +7831,6 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 	{
 		if (ccls != nullptr)
 		{
-			// [ZZ] substitute ccls for String internal type.
 			if (!ccls->IsKindOf(RUNTIME_CLASS(PClass)) || static_cast<PClass *>(ccls)->bExported)
 			{
 				cls = ccls;
@@ -7717,6 +7859,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 								Self = new FxSelf(ScriptPosition);
 								Self->ValueType = NewPointer(cls);
 							}
+							else novirtual = false;
 						}
 					}
 				}
@@ -7757,7 +7900,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		{
 			if (ArgList.Size() > 0)
 			{
-				ScriptPosition.Message(MSG_ERROR, "too many parameters in call to %s", MethodName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Too many parameters in call to %s", MethodName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -7801,7 +7944,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		{
 			if (ArgList.Size() > 0)
 			{
-				ScriptPosition.Message(MSG_ERROR, "too many parameters in call to %s", MethodName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Too many parameters in call to %s", MethodName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -7895,7 +8038,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		{
 			if (ArgList.Size() > 0)
 			{
-				ScriptPosition.Message(MSG_ERROR, "too many parameters in call to %s", MethodName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Too many parameters in call to %s", MethodName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -7945,7 +8088,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		auto x = new FxGetParentClass(Self);
 		return x->Resolve(ctx);
 	}
-	
+
 	if (Self->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)) && !Self->ValueType->IsKindOf(RUNTIME_CLASS(PClassPointer)))
 	{
 		auto ptype = static_cast<PPointer *>(Self->ValueType)->PointedType;
@@ -7955,7 +8098,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 			{
 				if (ArgList.Size() > 0)
 				{
-					ScriptPosition.Message(MSG_ERROR, "too many parameters in call to %s", MethodName.GetChars());
+					ScriptPosition.Message(MSG_ERROR, "Too many parameters in call to %s", MethodName.GetChars());
 					delete this;
 					return nullptr;
 				}
@@ -7968,7 +8111,7 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 		}
 		else
 		{
-			ScriptPosition.Message(MSG_ERROR, "Left hand side of %s must point to a class object\n", MethodName.GetChars());
+			ScriptPosition.Message(MSG_ERROR, "Left hand side of %s must point to a class object", MethodName.GetChars());
 			delete this;
 			return nullptr;
 		}
@@ -7976,22 +8119,15 @@ FxExpression *FxMemberFunctionCall::Resolve(FCompileContext& ctx)
 	else if (Self->ValueType->IsKindOf(RUNTIME_CLASS(PStruct)))
 	{
 		bool writable;
-		if (Self->RequestAddress(ctx, &writable) && writable)
-		{
-			cls = static_cast<PStruct*>(Self->ValueType);
-			Self->ValueType = NewPointer(Self->ValueType);
-		}
-		else
-		{
-			// Cannot be made writable so we cannot use its methods.
-			ScriptPosition.Message(MSG_ERROR, "Invalid expression on left hand side of %s\n", MethodName.GetChars());
-			delete this;
-			return nullptr;
-		}
+
+		// [ZZ] allow const method to be called on a readonly struct
+		isreadonly = !(Self->RequestAddress(ctx, &writable) && writable);
+		cls = static_cast<PStruct*>(Self->ValueType);
+		Self->ValueType = NewPointer(Self->ValueType);
 	}
 	else
 	{
-		ScriptPosition.Message(MSG_ERROR, "Invalid expression on left hand side of %s\n", MethodName.GetChars());
+		ScriptPosition.Message(MSG_ERROR, "Invalid expression on left hand side of %s", MethodName.GetChars());
 		delete this;
 		return nullptr;
 	}
@@ -8009,7 +8145,50 @@ isresolved:
 
 	if (afd == nullptr)
 	{
-		ScriptPosition.Message(MSG_ERROR, "Unknown function %s\n", MethodName.GetChars());
+		ScriptPosition.Message(MSG_ERROR, "Unknown function %s", MethodName.GetChars());
+		delete this;
+		return nullptr;
+	}
+
+	if (isreadonly && !(afd->Variants[0].Flags & VARF_ReadOnly))
+	{
+		// Cannot be made writable so we cannot use its methods.
+		// [ZZ] Why this esoteric message?
+		ScriptPosition.Message(MSG_ERROR, "Readonly struct on left hand side of %s not allowed", MethodName.GetChars());
+		delete this;
+		return nullptr;
+	}
+
+	// [ZZ] if self is a struct or a class member, check if it's valid to call this function at all.
+	//		implement more magic
+	int outerflags = 0;
+	if (ctx.Function)
+	{
+		outerflags = ctx.Function->Variants[0].Flags;
+		if (((outerflags & (VARF_VirtualScope | VARF_Virtual)) == (VARF_VirtualScope | VARF_Virtual)) && ctx.Class)
+			outerflags = FScopeBarrier::FlagsFromSide(FScopeBarrier::SideFromObjectFlags(ctx.Class->ObjectFlags));
+	}
+	int innerflags = afd->Variants[0].Flags;
+	int innerside = FScopeBarrier::SideFromFlags(innerflags);
+	// [ZZ] check this at compile time. this would work for most legit cases.
+	if (innerside == FScopeBarrier::Side_Virtual)
+	{
+		innerside = FScopeBarrier::SideFromObjectFlags(cls->ObjectFlags);
+		innerflags = FScopeBarrier::FlagsFromSide(innerside);
+	}
+	else if (innerside != FScopeBarrier::Side_Clear)
+	{
+		if (Self->ExprType == EFX_StructMember)
+		{
+			FxStructMember* pmember = (FxStructMember*)Self;
+			if (innerside == FScopeBarrier::Side_PlainData)
+				innerflags = FScopeBarrier::ChangeSideInFlags(innerflags, pmember->BarrierSide);
+		}
+	}
+	FScopeBarrier scopeBarrier(outerflags, innerflags, MethodName.GetChars());
+	if (!scopeBarrier.callable)
+	{
+		ScriptPosition.Message(MSG_ERROR, "%s", scopeBarrier.callerror.GetChars());
 		delete this;
 		return nullptr;
 	}
@@ -8022,14 +8201,14 @@ isresolved:
 			auto ccls = dyn_cast<PClass>(cls);
 			if (clstype == nullptr || ccls == nullptr || !clstype->IsDescendantOf(ccls))
 			{
-				ScriptPosition.Message(MSG_ERROR, "Cannot call non-static function %s::%s from here\n", cls->TypeName.GetChars(), MethodName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Cannot call non-static function %s::%s from here", cls->TypeName.GetChars(), MethodName.GetChars());
 				delete this;
 				return nullptr;
 			}
 			else
 			{
 				// Todo: If this is a qualified call to a parent class function, let it through (but this needs to disable virtual calls later.)
-				ScriptPosition.Message(MSG_ERROR, "Qualified member call to parent class %s::%s is not yet implemented\n", cls->TypeName.GetChars(), MethodName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Qualified member call to parent class %s::%s is not yet implemented", cls->TypeName.GetChars(), MethodName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -8057,7 +8236,7 @@ isresolved:
 			// Functions with no Actor usage may not be called through a pointer because they will lose their context.
 			if (!(afd->Variants[0].UseFlags & SUF_ACTOR))
 			{
-				ScriptPosition.Message(MSG_ERROR, "Function %s cannot be used with a non-self object\n", afd->SymbolName.GetChars());
+				ScriptPosition.Message(MSG_ERROR, "Function %s cannot be used with a non-self object", afd->SymbolName.GetChars());
 				delete this;
 				return nullptr;
 			}
@@ -8264,6 +8443,7 @@ FxVMFunctionCall::FxVMFunctionCall(FxExpression *self, PFunction *func, FArgumen
 	ArgList = std::move(args);
 	EmitTail = false;
 	NoVirtual = novirtual;
+	CallingFunction = nullptr;
 }
 
 //==========================================================================
@@ -8337,6 +8517,7 @@ FxExpression *FxVMFunctionCall::Resolve(FCompileContext& ctx)
 		return nullptr;
 	}
 
+	CallingFunction = ctx.Function;
 	if (ArgList.Size() > 0)
 	{
 		bool foundvarargs = false;
@@ -8544,6 +8725,17 @@ ExpEmit FxVMFunctionCall::Emit(VMFunctionBuilder *build)
 	ExpEmit selfemit;
 	if (Function->Variants[0].Flags & VARF_Method)
 	{
+#if 0
+		// [ZZ]
+		if (Function->Variants[0].Implementation && Function->Variants[0].Implementation->BarrierSide == FScopeBarrier::Side_Virtual)
+		{
+			// pass this even before Self, because otherwise we can't silently advance the arguments.
+			// this is not even implicit arguments.
+			build->Emit(OP_PARAM, 0, REGT_POINTER | REGT_KONST, build->GetConstantAddress(Function, ATAG_OBJECT));
+			build->Emit(OP_PARAM, 0, REGT_POINTER | REGT_KONST, build->GetConstantAddress(CallingFunction, ATAG_OBJECT));
+			count += 2;
+		}
+#endif
 		assert(Self != nullptr);
 		selfemit = Self->Emit(build);
 		assert((selfemit.RegType == REGT_POINTER) || (selfemit.Fixed && selfemit.Target));
diff --git a/src/scripting/backend/codegen.h b/src/scripting/backend/codegen.h
index abbcbd54e..000688341 100644
--- a/src/scripting/backend/codegen.h
+++ b/src/scripting/backend/codegen.h
@@ -45,6 +45,7 @@
 #include "s_sound.h"
 #include "actor.h"
 #include "vmbuilder.h"
+#include "scopebarrier.h"
 
 
 #define CHECKRESOLVED() if (isresolved) return this; isresolved=true;
@@ -95,7 +96,7 @@ struct FCompileContext
 
 	void HandleJumps(int token, FxExpression *handler);
 	void CheckReturn(PPrototype *proto, FScriptPosition &pos);
-	bool CheckReadOnly(int flags);
+	bool CheckWritable(int flags);
 	FxLocalVariableDeclaration *FindLocalVariable(FName name);
 };
 
@@ -1208,6 +1209,7 @@ private:
 class FxNew : public FxExpression
 {
 	FxExpression *val;
+	PFunction *CallingFunction;
 
 public:
 
@@ -1326,6 +1328,7 @@ public:
 	PField *membervar;
 	bool AddressRequested = false;
 	bool AddressWritable = true;
+	int BarrierSide = -1; // [ZZ] some magic
 	FxMemberBase(EFxType type, PField *f, const FScriptPosition &p);
 };
 
@@ -1707,6 +1710,7 @@ class FxVMFunctionCall : public FxExpression
 	// for multi assignment
 	int AssignCount = 0;
 	TArray<ExpEmit> ReturnRegs;
+	PFunction *CallingFunction;
 
 public:
 	FxVMFunctionCall(FxExpression *self, PFunction *func, FArgumentList &args, const FScriptPosition &pos, bool novirtual);
diff --git a/src/scripting/backend/scopebarrier.cpp b/src/scripting/backend/scopebarrier.cpp
new file mode 100644
index 000000000..4d9d6d2fc
--- /dev/null
+++ b/src/scripting/backend/scopebarrier.cpp
@@ -0,0 +1,152 @@
+#include "scopebarrier.h"
+#include "dobject.h"
+
+
+// Note: the same object can't be both UI and Play. This is checked explicitly in the field construction and will cause esoteric errors here if found.
+int FScopeBarrier::SideFromFlags(int flags)
+{
+	if (flags & VARF_UI)
+		return Side_UI;
+	if (flags & VARF_Play)
+		return Side_Play;
+	if (flags & VARF_VirtualScope)
+		return Side_Virtual;
+	if (flags & VARF_ClearScope)
+		return Side_Clear;
+	return Side_PlainData;
+}
+
+// same as above, but from object flags
+int FScopeBarrier::SideFromObjectFlags(int flags)
+{
+	if (flags & OF_UI)
+		return Side_UI;
+	if (flags & OF_Play)
+		return Side_Play;
+	return Side_PlainData;
+}
+
+//
+int FScopeBarrier::FlagsFromSide(int side)
+{
+	switch (side)
+	{
+	case Side_Play:
+		return VARF_Play;
+	case Side_UI:
+		return VARF_UI;
+	case Side_Virtual:
+		return VARF_VirtualScope;
+	case Side_Clear:
+		return VARF_ClearScope;
+	default:
+		return 0;
+	}
+}
+
+// used for errors
+const char* FScopeBarrier::StringFromSide(int side)
+{
+	switch (side)
+	{
+	case Side_PlainData:
+		return "data";
+	case Side_UI:
+		return "ui";
+	case Side_Play:
+		return "play";
+	case Side_Virtual:
+		return "virtualscope"; // should not happen!
+	case Side_Clear:
+		return "clearscope"; // should not happen!
+	default:
+		return "unknown";
+	}
+}
+
+// this modifies VARF_ flags and sets the side properly.
+int FScopeBarrier::ChangeSideInFlags(int flags, int side)
+{
+	flags &= ~(VARF_UI | VARF_Play | VARF_VirtualScope | VARF_ClearScope);
+	flags |= FlagsFromSide(side);
+	return flags;
+}
+
+FScopeBarrier::FScopeBarrier()
+{
+	sidefrom = -1;
+	sidelast = -1;
+	callable = true;
+	readable = true;
+	writable = true;
+}
+
+FScopeBarrier::FScopeBarrier(int flags1, int flags2, const char* name)
+{
+	sidefrom = -1;
+	sidelast = -1;
+	callable = true;
+	readable = true;
+	writable = true;
+
+	AddFlags(flags1, flags2, name);
+}
+
+// AddFlags modifies ALLOWED actions by flags1->flags2.
+// This is used for comparing a.b.c.d access - if non-allowed field is seen anywhere in the chain, anything after it is non-allowed.
+// This struct is used so that the logic is in a single place.
+void FScopeBarrier::AddFlags(int flags1, int flags2, const char* name)
+{
+	// note: if it's already non-readable, don't even try advancing
+	if (!readable)
+		return;
+
+	// we aren't interested in any other flags
+	//  - update: including VARF_VirtualScope. inside the function itself, we treat it as if it's PlainData.
+	flags1 &= VARF_UI | VARF_Play;
+	flags2 &= VARF_UI | VARF_Play | VARF_ReadOnly;
+
+	if (sidefrom < 0) sidefrom = SideFromFlags(flags1);
+	if (sidelast < 0) sidelast = sidefrom;
+
+	// flags1 = what's trying to access
+	// flags2 = what's being accessed
+
+	int sideto = SideFromFlags(flags2);
+
+	// plain data inherits whatever scope modifiers that context or field container has.
+	// i.e. play String bla; is play, and all non-specified methods/fields inside it are play as well.
+	if (sideto != Side_PlainData)
+		sidelast = sideto;
+	else sideto = sidelast;
+
+	if ((sideto == Side_UI) && (sidefrom != Side_UI)) // only ui -> ui is readable
+	{
+		readable = false;
+		if (name) readerror.Format("Can't read %s field %s from %s context", StringFromSide(sideto), name, StringFromSide(sidefrom));
+	}
+
+	if (!readable)
+	{
+		writable = false;
+		callable = false;
+		if (name)
+		{
+			writeerror.Format("Can't write %s field %s from %s context (not readable)", StringFromSide(sideto), name, StringFromSide(sidefrom));
+			callerror.Format("Can't call %s function %s from %s context (not readable)", StringFromSide(sideto), name, StringFromSide(sidefrom));
+		}
+		return;
+	}
+
+	if (writable && (sidefrom != sideto)) // only matching types are writable (plain data implicitly takes context type by default, unless overridden)
+	{
+		writable = false;
+		if (name) writeerror.Format("Can't write %s field %s from %s context", StringFromSide(sideto), name, StringFromSide(sidefrom));
+	}
+
+	if (callable && (sidefrom != sideto) && !(flags2 & VARF_ReadOnly)) // readonly on methods is used for plain data stuff that can be called from ui/play context.
+	{
+		callable = false;
+		if (name) callerror.Format("Can't call %s function %s from %s context", StringFromSide(sideto), name, StringFromSide(sidefrom));
+	}
+}
diff --git a/src/scripting/backend/scopebarrier.h b/src/scripting/backend/scopebarrier.h
new file mode 100644
index 000000000..ed4f25a10
--- /dev/null
+++ b/src/scripting/backend/scopebarrier.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include "zstring.h"
+
+//
+// [ZZ] this really should be in codegen.h, but vmexec needs to access it
+struct FScopeBarrier
+{
+	bool callable;
+	bool readable;
+	bool writable;
+
+	// this is the error message
+	FString callerror;
+	FString readerror;
+	FString writeerror;
+
+	// this is used to make the error message.
+	enum Side
+	{
+		Side_PlainData = 0,
+		Side_UI = 1,
+		Side_Play = 2,
+		Side_Virtual = 3, // do NOT change the value
+		Side_Clear = 4
+	};
+	int sidefrom;
+	int sidelast;
+
+	// Note: the same object can't be both UI and Play. This is checked explicitly in the field construction and will cause esoteric errors here if found.
+	static int SideFromFlags(int flags);
+
+	// same as above, but from object flags
+	static int SideFromObjectFlags(int flags);
+
+	//
+	static int FlagsFromSide(int side);
+	
+	// used for errors
+	static const char* StringFromSide(int side);
+
+	// this modifies VARF_ flags and sets the side properly.
+	static int ChangeSideInFlags(int flags, int side);
+	FScopeBarrier();
+	FScopeBarrier(int flags1, int flags2, const char* name);
+
+	// AddFlags modifies ALLOWED actions by flags1->flags2.
+	// This is used for comparing a.b.c.d access - if non-allowed field is seen anywhere in the chain, anything after it is non-allowed.
+	// This struct is used so that the logic is in a single place.
+	void AddFlags(int flags1, int flags2, const char* name);
+};
+
diff --git a/src/scripting/thingdef.cpp b/src/scripting/thingdef.cpp
index d0b7df449..c0e444893 100644
--- a/src/scripting/thingdef.cpp
+++ b/src/scripting/thingdef.cpp
@@ -110,12 +110,13 @@ void SetImplicitArgs(TArray<PType *> *args, TArray<DWORD> *argflags, TArray<FNam
 	if (funcflags & VARF_Method)
 	{
 		// implied self pointer
-		if (args != nullptr)		args->Push(NewPointer(cls)); 
+		if (args != nullptr)		args->Push(NewPointer(cls, !!(funcflags & VARF_ReadOnly))); 
 		if (argflags != nullptr)	argflags->Push(VARF_Implicit | VARF_ReadOnly);
 		if (argnames != nullptr)	argnames->Push(NAME_self);
 	}
 	if (funcflags & VARF_Action)
 	{
+		assert(!(funcflags & VARF_ReadOnly));
 		// implied caller and callingstate pointers
 		if (args != nullptr)
 		{
@@ -163,6 +164,10 @@ PFunction *CreateAnonymousFunction(PClass *containingclass, PType *returntype, i
 	// Functions that only get flagged for actors do not need the additional two context parameters.
 	int fflags = (flags& (SUF_OVERLAY | SUF_WEAPON | SUF_ITEM)) ? VARF_Action | VARF_Method : VARF_Method;
 
+	// [ZZ] give anonymous functions the scope of their class 
+	//      (just give them VARF_Play, whatever)
+	fflags |= VARF_Play;
+
 	rets[0] = returntype != nullptr? returntype : TypeError;	// Use TypeError as placeholder if we do not know the return type yet.
 	SetImplicitArgs(&args, &argflags, &argnames, containingclass, fflags, flags);
 
@@ -194,7 +199,7 @@ PFunction *FindClassMemberFunction(PStruct *selfcls, PStruct *funccls, FName nam
 		{
 			sc.Message(MSG_ERROR, "%s is not a member function of %s", name.GetChars(), selfcls->TypeName.GetChars());
 		}
-		else if (funcsym->Variants[0].Flags & VARF_Private && symtable != &funccls->Symbols)
+		else if ((funcsym->Variants[0].Flags & VARF_Private) && symtable != &funccls->Symbols)
 		{
 			// private access is only allowed if the symbol table belongs to the class in which the current function is being defined.
 			sc.Message(MSG_ERROR, "%s is declared private and not accessible", symbol->SymbolName.GetChars());
diff --git a/src/scripting/thingdef_data.cpp b/src/scripting/thingdef_data.cpp
index c50b7f65b..a09134d58 100644
--- a/src/scripting/thingdef_data.cpp
+++ b/src/scripting/thingdef_data.cpp
@@ -858,8 +858,8 @@ void InitThingdef()
 	// 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(linestruct, false)), false), myoffsetof(sector_t, Lines), VARF_Native);
 
-	sectorstruct->AddNativeField("ceilingplane", secplanestruct, myoffsetof(sector_t, ceilingplane), VARF_Native);
-	sectorstruct->AddNativeField("floorplane", secplanestruct, myoffsetof(sector_t, floorplane), VARF_Native);
+	sectorstruct->AddNativeField("ceilingplane", secplanestruct, myoffsetof(sector_t, ceilingplane), VARF_Native | VARF_ReadOnly);
+	sectorstruct->AddNativeField("floorplane", secplanestruct, myoffsetof(sector_t, floorplane), VARF_Native | VARF_ReadOnly);
 
 
 
diff --git a/src/scripting/vm/vm.h b/src/scripting/vm/vm.h
index cda7a1c58..06de1e2c1 100644
--- a/src/scripting/vm/vm.h
+++ b/src/scripting/vm/vm.h
@@ -8,6 +8,10 @@
 #include "doomerrors.h"
 #include "memarena.h"
 
+// [ZZ] there are serious circular references between this and the rest of ZScript code, so it needs to be done like this
+//		these are used in vmexec.h
+void FScopeBarrier_ValidateNew(PClass* cls, PFunction* callingfunc);
+void FScopeBarrier_ValidateCall(PFunction* calledfunc, PFunction* callingfunc, PClass* selftype);
 class DObject;
 
 extern FMemArena ClassDataAllocator;
@@ -704,6 +708,8 @@ public:
 	bool Native;
 	bool Final = false;				// cannot be overridden
 	bool Unsafe = false;			// Contains references to class fields that are unsafe for psp and item state calls.
+	bool FuncConst = false;			// [ZZ] readonly function
+	int BarrierSide = 0;			// [ZZ] FScopeBarrier::Side
 	BYTE ImplicitArgs = 0;	// either 0 for static, 1 for method or 3 for action
 	unsigned VirtualIndex = ~0u;
 	FName Name;
@@ -712,7 +718,7 @@ public:
 
 	class PPrototype *Proto;
 
-	VMFunction(FName name = NAME_None) : Native(false), ImplicitArgs(0), Name(name), Proto(NULL) 
+	VMFunction(FName name = NAME_None) : Native(false), ImplicitArgs(0), Name(name), Proto(NULL)
 	{
 		AllFunctions.Push(this);
 	}
diff --git a/src/scripting/vm/vmexec.h b/src/scripting/vm/vmexec.h
index c37e29cbf..cd3925adc 100644
--- a/src/scripting/vm/vmexec.h
+++ b/src/scripting/vm/vmexec.h
@@ -664,13 +664,27 @@ begin:
 			VMReturn returns[MAX_RETURNS];
 			int numret;
 
+			b = B;
+#if 0
+			// [ZZ] hax!
+			if (call->BarrierSide == 3) // :( - this is Side_Virtual. Side_Virtual should receive special arguments.
+			{
+				PFunction* calledfunc = (PFunction*)(reg.param + f->NumParam - b)[0].a;
+				PFunction* callingfunc = (PFunction*)(reg.param + f->NumParam - b)[1].a;
+				DObject* dobj = (DObject*)(reg.param + f->NumParam - b)[2].a; // this is the self pointer. it should be in, since Side_Virtual functions are always non-static methods.
+				PClass* selftype = dobj->GetClass();
+				FScopeBarrier_ValidateCall(calledfunc, callingfunc, selftype);
+				b -= 2;
+			}
+#endif
+
 			FillReturns(reg, f, returns, pc+1, C);
 			if (call->Native)
 			{
 				try
 				{
 					VMCycles[0].Unclock();
-					numret = static_cast<VMNativeFunction *>(call)->NativeCall(reg.param + f->NumParam - B, call->DefaultArgs, B, returns, C);
+					numret = static_cast<VMNativeFunction *>(call)->NativeCall(reg.param + f->NumParam - b, call->DefaultArgs, b, returns, C);
 					VMCycles[0].Clock();
 				}
 				catch (CVMAbortException &err)
@@ -686,7 +700,7 @@ begin:
 				VMCalls[0]++;
 				VMScriptFunction *script = static_cast<VMScriptFunction *>(call);
 				VMFrame *newf = stack->AllocFrame(script);
-				VMFillParams(reg.param + f->NumParam - B, newf, B);
+				VMFillParams(reg.param + f->NumParam - b, newf, b);
 				try
 				{
 					numret = Exec(stack, script->Code, returns, C);
@@ -803,7 +817,11 @@ begin:
 	{
 		b = B;
 		PClass *cls = (PClass*)(pc->op == OP_NEW ? reg.a[b] : konsta[b].v);
+		PFunction *callingfunc = (PFunction*)konsta[C].o; // [ZZ] due to how this is set, it's always const
 		if (cls->ObjectFlags & OF_Abstract) ThrowAbortException(X_OTHER, "Cannot instantiate abstract class %s", cls->TypeName.GetChars());
+		// [ZZ] validate readonly and between scope construction
+		if (callingfunc)
+			FScopeBarrier_ValidateNew(cls, callingfunc);
 		reg.a[a] = cls->CreateNew();
 		reg.atag[a] = ATAG_OBJECT;
 		NEXTOP;
diff --git a/src/scripting/zscript/zcc-parse.lemon b/src/scripting/zscript/zcc-parse.lemon
index 6d3e8a856..f80a09974 100644
--- a/src/scripting/zscript/zcc-parse.lemon
+++ b/src/scripting/zscript/zcc-parse.lemon
@@ -213,6 +213,8 @@ class_ancestry(X) ::= COLON dottable_id(A).	{ X = A; /*X-overwrites-A*/ }
 class_flags(X) ::= .										{ X.Flags = 0; X.Replaces = NULL; }
 class_flags(X) ::= class_flags(A) ABSTRACT.					{ X.Flags = A.Flags | ZCC_Abstract; X.Replaces = A.Replaces; }
 class_flags(X) ::= class_flags(A) NATIVE.					{ X.Flags = A.Flags | ZCC_Native; X.Replaces = A.Replaces; }
+class_flags(X) ::= class_flags(A) UI.						{ X.Flags = A.Flags | ZCC_UIFlag; X.Replaces = A.Replaces; }
+class_flags(X) ::= class_flags(A) PLAY.						{ X.Flags = A.Flags | ZCC_Play; X.Replaces = A.Replaces; }
 class_flags(X) ::= class_flags(A) REPLACES dottable_id(B).	{ X.Flags = A.Flags; X.Replaces = B; }
 
 /*----- Dottable Identifier -----*/
@@ -326,7 +328,9 @@ struct_def(X) ::= STRUCT(T) IDENTIFIER(A) struct_flags(S) LBRACE opt_struct_body
 
 %type struct_flags{ClassFlagsBlock}
 struct_flags(X) ::= .										{ X.Flags = 0; }
-struct_flags(X) ::= NATIVE.									{ X.Flags = ZCC_Native; }
+struct_flags(X) ::= struct_flags(A) UI.						{ X.Flags = A.Flags | ZCC_UIFlag; }
+struct_flags(X) ::= struct_flags(A) PLAY.					{ X.Flags = A.Flags | ZCC_Play; }
+struct_flags(X) ::= struct_flags(A) NATIVE.					{ X.Flags = A.Flags | ZCC_Native; }
 
 opt_struct_body(X) ::= .								{ X = NULL; }
 opt_struct_body(X) ::= struct_body(X).
@@ -999,6 +1003,10 @@ decl_flag(X) ::= DEPRECATED(T).	{ X.Int = ZCC_Deprecated; X.SourceLoc =  T.Sourc
 decl_flag(X) ::= VIRTUAL(T).	{ X.Int = ZCC_Virtual; X.SourceLoc =  T.SourceLoc; }
 decl_flag(X) ::= OVERRIDE(T).	{ X.Int = ZCC_Override; X.SourceLoc =  T.SourceLoc; }
 decl_flag(X) ::= VARARG(T).     { X.Int = ZCC_VarArg; X.SourceLoc = T.SourceLoc; }
+decl_flag(X) ::= UI(T).			{ X.Int = ZCC_UIFlag; X.SourceLoc = T.SourceLoc; }
+decl_flag(X) ::= PLAY(T).		{ X.Int = ZCC_Play; X.SourceLoc = T.SourceLoc; }
+decl_flag(X) ::= CLEARSCOPE(T). { X.Int = ZCC_ClearScope; X.SourceLoc = T.SourceLoc; }
+decl_flag(X) ::= VIRTUALSCOPE(T). { X.Int = ZCC_VirtualScope; X.SourceLoc = T.SourceLoc; }
 
 func_const(X) ::= .							{ X.Int = 0; X.SourceLoc = stat->sc->GetMessageLine(); }
 func_const(X) ::= CONST(T).					{ X.Int = ZCC_FuncConst; X.SourceLoc = T.SourceLoc; }
diff --git a/src/scripting/zscript/zcc_compile.cpp b/src/scripting/zscript/zcc_compile.cpp
index 5574fcc18..f8e9980a2 100644
--- a/src/scripting/zscript/zcc_compile.cpp
+++ b/src/scripting/zscript/zcc_compile.cpp
@@ -495,6 +495,16 @@ void ZCCCompiler::CreateStructTypes()
 		{
 			s->strct->Type = NewStruct(s->NodeName(), outer);
 		}
+
+		if ((s->strct->Flags & (ZCC_UIFlag | ZCC_Play)) == (ZCC_UIFlag | ZCC_Play))
+		{
+			Error(s->strct, "Struct %s has incompatible flags", s->NodeName().GetChars());
+		}
+
+		if (s->strct->Flags & ZCC_UIFlag)
+			s->Type()->ObjectFlags |= OF_UI;
+		if (s->strct->Flags & ZCC_Play)
+			s->Type()->ObjectFlags |= OF_Play;
 		s->strct->Symbol = new PSymbolType(s->NodeName(), s->Type());
 		syms->AddSymbol(s->strct->Symbol);
 
@@ -597,11 +607,33 @@ void ZCCCompiler::CreateClassTypes()
 						c->cls->Type = nullptr;
 					}
 				}
-				if (c->cls->Flags & ZCC_Abstract)
-				{
-					c->Type()->ObjectFlags |= OF_Abstract;
-				}
 				if (c->Type() == nullptr) c->cls->Type = parent->FindClassTentative(c->NodeName());
+				if (c->cls->Flags & ZCC_Abstract)
+					c->Type()->ObjectFlags |= OF_Abstract;
+				// 
+				static int incompatible[] = { ZCC_UIFlag, ZCC_Play, ZCC_ClearScope };
+				int incompatiblecnt = 0;
+				for (size_t k = 0; k < countof(incompatible); k++)
+					if (incompatible[k] & c->cls->Flags) incompatiblecnt++;
+				
+				if (incompatiblecnt > 1)
+				{
+					Error(c->cls, "Class %s has incompatible flags", c->NodeName().GetChars());
+				}
+				
+				if (c->cls->Flags & ZCC_UIFlag)
+					c->Type()->ObjectFlags = (c->Type()->ObjectFlags&~OF_Play) | OF_UI;
+				if (c->cls->Flags & ZCC_Play)
+					c->Type()->ObjectFlags = (c->Type()->ObjectFlags&~OF_UI) | OF_Play;
+				if (parent->ObjectFlags & (OF_UI | OF_Play)) // parent is either ui or play
+				{
+					if (c->cls->Flags & (ZCC_UIFlag | ZCC_Play))
+					{
+						Error(c->cls, "Can't change class scope in class %s", c->NodeName().GetChars());
+					}
+					c->Type()->ObjectFlags = (c->Type()->ObjectFlags & ~(OF_UI | OF_Play)) | (parent->ObjectFlags & (OF_UI | OF_Play));
+				}
+
 				c->Type()->bExported = true;	// this class is accessible to script side type casts. (The reason for this flag is that types like PInt need to be skipped.)
 				c->cls->Symbol = new PSymbolType(c->NodeName(), c->Type());
 				OutNamespace->Symbols.AddSymbol(c->cls->Symbol);
@@ -1050,8 +1082,8 @@ bool ZCCCompiler::CompileFields(PStruct *type, TArray<ZCC_VarDeclarator *> &Fiel
 
 		// For structs only allow 'deprecated', for classes exclude function qualifiers.
 		int notallowed = forstruct? 
-			ZCC_Latent | ZCC_Final | ZCC_Action | ZCC_Static | ZCC_FuncConst | ZCC_Abstract | ZCC_Virtual | ZCC_Override | ZCC_Meta | ZCC_Extension :
-			ZCC_Latent | ZCC_Final | ZCC_Action | ZCC_Static | ZCC_FuncConst | ZCC_Abstract | ZCC_Virtual | ZCC_Override | ZCC_Extension;
+			ZCC_Latent | ZCC_Final | ZCC_Action | ZCC_Static | ZCC_FuncConst | ZCC_Abstract | ZCC_Virtual | ZCC_Override | ZCC_Meta | ZCC_Extension | ZCC_VirtualScope | ZCC_ClearScope :
+			ZCC_Latent | ZCC_Final | ZCC_Action | ZCC_Static | ZCC_FuncConst | ZCC_Abstract | ZCC_Virtual | ZCC_Override | ZCC_Extension | ZCC_VirtualScope | ZCC_ClearScope;
 
 		if (field->Flags & notallowed)
 		{
@@ -1066,12 +1098,39 @@ bool ZCCCompiler::CompileFields(PStruct *type, TArray<ZCC_VarDeclarator *> &Fiel
 		if (field->Flags & ZCC_Deprecated) varflags |= VARF_Deprecated;
 		if (field->Flags & ZCC_ReadOnly) varflags |= VARF_ReadOnly;
 		if (field->Flags & ZCC_Transient) varflags |= VARF_Transient;
+		if (type->ObjectFlags & OF_UI)
+			varflags |= VARF_UI;
+		if (type->ObjectFlags & OF_Play)
+			varflags |= VARF_Play;
+		if (field->Flags & ZCC_UIFlag)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_UI);
+		if (field->Flags & ZCC_Play)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_Play);
+		if (field->Flags & ZCC_ClearScope)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_PlainData);
 
 		if (field->Flags & ZCC_Native)
 		{
 			varflags |= VARF_Native | VARF_Transient;
 		}
 
+		static int excludescope[] = { ZCC_UIFlag, ZCC_Play, ZCC_ClearScope };
+		int excludeflags = 0;
+		int fc = 0;
+		for (size_t i = 0; i < countof(excludescope); i++)
+		{
+			if (field->Flags & excludescope[i])
+			{
+				fc++;
+				excludeflags |= excludescope[i];
+			}
+		}
+		if (fc > 1)
+		{
+			Error(field, "Invalid combination of scope qualifiers %s on field %s", FlagsToString(excludeflags).GetChars(), FName(field->Names->Name).GetChars());
+			varflags &= ~(VARF_UI | VARF_Play); // make plain data
+		}
+
 		if (field->Flags & ZCC_Meta)
 		{
 			varflags |= VARF_Meta | VARF_Static | VARF_ReadOnly;	// metadata implies readonly
@@ -1121,7 +1180,7 @@ bool ZCCCompiler::CompileFields(PStruct *type, TArray<ZCC_VarDeclarator *> &Fiel
 				}
 				else if (hasnativechildren)
 				{
-					Error(field, "Cannot add field %s to %s. %s has native children which means it size may not change.", FName(name->Name).GetChars(), type->TypeName.GetChars(), type->TypeName.GetChars());
+					Error(field, "Cannot add field %s to %s. %s has native children which means it size may not change", FName(name->Name).GetChars(), type->TypeName.GetChars(), type->TypeName.GetChars());
 				}
 				else
 				{
@@ -1218,7 +1277,7 @@ bool ZCCCompiler::CompileProperties(PClass *type, TArray<ZCC_Property *> &Proper
 FString ZCCCompiler::FlagsToString(uint32_t flags)
 {
 
-	const char *flagnames[] = { "native", "static", "private", "protected", "latent", "final", "meta", "action", "deprecated", "readonly", "funcconst", "abstract", "extension", "virtual", "override", "transient", "vararg" };
+	const char *flagnames[] = { "native", "static", "private", "protected", "latent", "final", "meta", "action", "deprecated", "readonly", "const", "abstract", "extend", "virtual", "override", "transient", "vararg", "ui", "play", "clearscope", "virtualscope" };
 	FString build;
 
 	for (size_t i = 0; i < countof(flagnames); i++)
@@ -2017,7 +2076,7 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 			} while (t != f->Type);
 		}
 
-		int notallowed = ZCC_Latent | ZCC_Meta | ZCC_ReadOnly | ZCC_FuncConst | ZCC_Abstract;
+		int notallowed = ZCC_Latent | ZCC_Meta | ZCC_ReadOnly | ZCC_Abstract;
 
 		if (f->Flags & notallowed)
 		{
@@ -2064,12 +2123,48 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 		if (f->Flags & ZCC_Virtual) varflags |= VARF_Virtual;
 		if (f->Flags & ZCC_Override) varflags |= VARF_Override;
 		if (f->Flags & ZCC_VarArg) varflags |= VARF_VarArg;
+		if (f->Flags & ZCC_FuncConst) varflags |= VARF_ReadOnly; // FuncConst method is internally marked as VARF_ReadOnly
+		if (c->Type()->ObjectFlags & OF_UI)
+			varflags |= VARF_UI;
+		if (c->Type()->ObjectFlags & OF_Play)
+			varflags |= VARF_Play;
+		if (f->Flags & ZCC_FuncConst)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_PlainData); // const implies clearscope. this is checked a bit later to also not have ZCC_Play/ZCC_UIFlag.
+		if (f->Flags & ZCC_UIFlag)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_UI);
+		if (f->Flags & ZCC_Play)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_Play);
+		if (f->Flags & ZCC_ClearScope)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_Clear);
+		if (f->Flags & ZCC_VirtualScope)
+			varflags = FScopeBarrier::ChangeSideInFlags(varflags, FScopeBarrier::Side_Virtual);
+
+		// [ZZ] supporting const self for actors is quite a cumbersome task because there's no concept of a const pointer (?)
+		//      either way, it doesn't make sense, because you can call any method on a readonly class instance.
+
+		// The above is nonsense. This needs to work and needs to be implemented properly.
+		/*
+		if ((f->Flags & ZCC_FuncConst) && (c->Type()->IsKindOf(RUNTIME_CLASS(PClass))))
+		{
+			Error(f, "'Const' on a method can only be used in structs");
+		}
+		*/
+
 		if ((f->Flags & ZCC_VarArg) && !(f->Flags & ZCC_Native))
 		{
 			Error(f, "'VarArg' can only be used with native methods");
 		}
 		if (f->Flags & ZCC_Action)
 		{
+			if (varflags & VARF_ReadOnly)
+			{
+				Error(f, "Action functions cannot be declared const");
+				varflags &= ~VARF_ReadOnly;
+			}
+			if (varflags & VARF_UI)
+			{
+				Error(f, "Action functions cannot be declared UI");
+			}
 			// Non-Actors cannot have action functions.
 			if (!c->Type()->IsKindOf(RUNTIME_CLASS(PClassActor)))
 			{
@@ -2089,36 +2184,69 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 		}
 		if (f->Flags & ZCC_Static) varflags = (varflags & ~VARF_Method) | VARF_Final, implicitargs = 0;	// Static implies Final.
 
-
 		if (varflags & VARF_Override) varflags &= ~VARF_Virtual;	// allow 'virtual override'.
 																	// Only one of these flags may be used.
 		static int exclude[] = { ZCC_Virtual, ZCC_Override, ZCC_Action, ZCC_Static };
-		static const char * print[] = { "virtual", "override", "action", "static" };
+		int excludeflags = 0;
 		int fc = 0;
-		FString build;
-		for (int i = 0; i < 4; i++)
+		for (size_t i = 0; i < countof(exclude); i++)
 		{
 			if (f->Flags & exclude[i])
 			{
 				fc++;
-				if (build.Len() > 0) build += ", ";
-				build += print[i];
+				excludeflags |= exclude[i];
 			}
 		}
 		if (fc > 1)
 		{
-			Error(f, "Invalid combination of qualifiers %s on function %s.", FName(f->Name).GetChars(), build.GetChars());
+			Error(f, "Invalid combination of qualifiers %s on function %s", FlagsToString(excludeflags).GetChars(), FName(f->Name).GetChars());
 			varflags |= VARF_Method;
 		}
 		if (varflags & VARF_Override) varflags |= VARF_Virtual;	// Now that the flags are checked, make all override functions virtual as well.
 
+		// [ZZ] this doesn't make sense either.
+		if ((varflags&(VARF_ReadOnly | VARF_Method)) == VARF_ReadOnly) // non-method const function
+		{
+			Error(f, "'Const' on a static method is not supported");
+		}
+
+		// [ZZ] neither this
+		if ((varflags&(VARF_VirtualScope | VARF_Method)) == VARF_VirtualScope) // non-method virtualscope function
+		{
+			Error(f, "'VirtualScope' on a static method is not supported");
+		}
+
+		// you can't have a const function belonging to either ui or play.
+		// const is intended for plain data to signify that you can call a method on readonly variable.
+		if ((f->Flags & ZCC_FuncConst) && (f->Flags & (ZCC_UIFlag | ZCC_Play | ZCC_VirtualScope)))
+		{
+			Error(f, "Invalid combination of qualifiers %s on function %s", FlagsToString(f->Flags&(ZCC_FuncConst | ZCC_UIFlag | ZCC_Play | ZCC_VirtualScope)).GetChars(), FName(f->Name).GetChars());
+		}
+
+		static int excludescope[] = { ZCC_UIFlag, ZCC_Play, ZCC_ClearScope, ZCC_VirtualScope };
+		excludeflags = 0;
+		fc = 0;
+		for (size_t i = 0; i < countof(excludescope); i++)
+		{
+			if (f->Flags & excludescope[i])
+			{
+				fc++;
+				excludeflags |= excludescope[i];
+			}
+		}
+		if (fc > 1)
+		{
+			Error(f, "Invalid combination of scope qualifiers %s on function %s", FlagsToString(excludeflags).GetChars(), FName(f->Name).GetChars());
+			varflags &= ~(VARF_UI | VARF_Play); // make plain data
+		}
+
 		if (f->Flags & ZCC_Native)
 		{
 			varflags |= VARF_Native;
 			afd = FindFunction(c->Type(), FName(f->Name).GetChars());
 			if (afd == nullptr)
 			{
-				Error(f, "The function '%s.%s' has not been exported from the executable.", c->Type()->TypeName.GetChars(), FName(f->Name).GetChars());
+				Error(f, "The function '%s.%s' has not been exported from the executable", c->Type()->TypeName.GetChars(), FName(f->Name).GetChars());
 			}
 			else
 			{
@@ -2232,7 +2360,7 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 					}
 					else if (hasoptionals)
 					{
-						Error(p, "All arguments after the first optional one need also be optional.");
+						Error(p, "All arguments after the first optional one need also be optional");
 					}
 					// TBD: disallow certain types? For now, let everything pass that isn't an array.
 					args.Push(type);
@@ -2287,18 +2415,26 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 			sym->Variants[0].Implementation->DefaultArgs = std::move(argdefaults);
 		}
 
+		if (sym->Variants[0].Implementation != nullptr)
+		{
+			// [ZZ] unspecified virtual function inherits old scope. virtual function scope can't be changed.
+			sym->Variants[0].Implementation->BarrierSide = FScopeBarrier::SideFromFlags(varflags);
+		}
+
 		PClass *clstype = static_cast<PClass *>(c->Type());
 		if (varflags & VARF_Virtual)
 		{
 			if (sym->Variants[0].Implementation == nullptr)
 			{
-				Error(f, "Virtual function %s.%s not present.", c->Type()->TypeName.GetChars(), FName(f->Name).GetChars());
+				Error(f, "Virtual function %s.%s not present", c->Type()->TypeName.GetChars(), FName(f->Name).GetChars());
 				return;
 			}
+			
 			if (varflags & VARF_Final)
-			{
 				sym->Variants[0].Implementation->Final = true;
-			}
+			if (varflags & VARF_ReadOnly)
+				sym->Variants[0].Implementation->FuncConst = true;
+
 			if (forclass)
 			{
 				int vindex = clstype->FindVirtualIndex(sym->SymbolName, sym->Variants[0].Proto);
@@ -2316,6 +2452,23 @@ void ZCCCompiler::CompileFunction(ZCC_StructWork *c, ZCC_FuncDeclarator *f, bool
 						{
 							Error(f, "Attempt to override final function %s", FName(f->Name).GetChars());
 						}
+						// you can't change ui/play/clearscope for a virtual method.
+						if (f->Flags & (ZCC_UIFlag|ZCC_Play|ZCC_ClearScope|ZCC_VirtualScope))
+						{
+							Error(f, "Attempt to change scope for virtual function %s", FName(f->Name).GetChars());
+						}
+						// you can't change const qualifier for a virtual method
+						if (oldfunc->FuncConst != sym->Variants[0].Implementation->FuncConst)
+						{
+							Error(f, "Attempt to change const qualifier for virtual function %s", FName(f->Name).GetChars());
+						}
+						// inherit scope of original function if override not specified
+						sym->Variants[0].Implementation->BarrierSide = oldfunc->BarrierSide;
+						sym->Variants[0].Flags = FScopeBarrier::ChangeSideInFlags(sym->Variants[0].Flags, oldfunc->BarrierSide);
+						// inherit const from original function
+						if ((sym->Variants[0].Implementation->FuncConst = oldfunc->FuncConst))
+							sym->Variants[0].Flags |= VARF_ReadOnly;
+													
 						clstype->Virtuals[vindex] = sym->Variants[0].Implementation;
 						sym->Variants[0].Implementation->VirtualIndex = vindex;
 					}
diff --git a/src/scripting/zscript/zcc_parser.cpp b/src/scripting/zscript/zcc_parser.cpp
index 439b495b4..761af9541 100644
--- a/src/scripting/zscript/zcc_parser.cpp
+++ b/src/scripting/zscript/zcc_parser.cpp
@@ -137,6 +137,10 @@ static void InitTokenMap()
 	TOKENDEF (TK_Latent,		ZCC_LATENT);
 	TOKENDEF (TK_Virtual,		ZCC_VIRTUAL);
 	TOKENDEF (TK_VarArg,        ZCC_VARARG);
+	TOKENDEF (TK_UI,			ZCC_UI);
+	TOKENDEF (TK_Play,			ZCC_PLAY);
+	TOKENDEF (TK_ClearScope,	ZCC_CLEARSCOPE);
+	TOKENDEF (TK_VirtualScope,  ZCC_VIRTUALSCOPE);
 	TOKENDEF (TK_Override,		ZCC_OVERRIDE);
 	TOKENDEF (TK_Final,			ZCC_FINAL);
 	TOKENDEF (TK_Meta,			ZCC_META);
diff --git a/src/scripting/zscript/zcc_parser.h b/src/scripting/zscript/zcc_parser.h
index 95bafd54f..c414c0e9c 100644
--- a/src/scripting/zscript/zcc_parser.h
+++ b/src/scripting/zscript/zcc_parser.h
@@ -36,7 +36,11 @@ enum
 	ZCC_Virtual			= 1 << 13,
 	ZCC_Override		= 1 << 14,
 	ZCC_Transient		= 1 << 15,
-	ZCC_VarArg			= 1 << 16
+	ZCC_VarArg			= 1 << 16,
+	ZCC_UIFlag			= 1 << 17, // there's also token called ZCC_UI
+	ZCC_Play			= 1 << 18,
+	ZCC_ClearScope		= 1 << 19,
+	ZCC_VirtualScope	= 1 << 20,
 };
 
 // Function parameter modifiers
diff --git a/src/zstring.h b/src/zstring.h
index b925a39b1..e486a0e8b 100644
--- a/src/zstring.h
+++ b/src/zstring.h
@@ -450,13 +450,4 @@ template<> struct THashTraits<FString>
 	int Compare(const FString &left, const FString &right) { return left.Compare(right); }
 };
 
-class FStringNoInit
-{
-	char mem[sizeof(FString)];
-	operator FString&() 
-	{
-		return *reinterpret_cast<FString*>(&mem);
-	}
-};
-
 #endif
diff --git a/wadsrc/static/zscript/actor.txt b/wadsrc/static/zscript/actor.txt
index ea17fecde..eb0a3895f 100644
--- a/wadsrc/static/zscript/actor.txt
+++ b/wadsrc/static/zscript/actor.txt
@@ -450,13 +450,13 @@ class Actor : Thinker native
 	native static int FindUniqueTid(int start = 0, int limit = 0);
 	native void SetShade(color col);
 		
-	native string GetTag(string defstr = "");
+	native string GetTag(string defstr = "") const;
 	native void SetTag(string defstr = "");
 	native double GetBobOffset(double frac = 0);
 	native void ClearCounters();
 	native bool GiveBody (int num, int max=0);
 	native bool HitFloor();
-	native bool isTeammate(Actor other);
+	native bool isTeammate(Actor other) const;
 	native int PlayerNumber();
 	native void SetFriendPlayer(PlayerInfo player);
 	native void SoundAlert(Actor target, bool splash = false, double maxdist = 0);
@@ -468,15 +468,15 @@ class Actor : Thinker native
 	native bool UpdateWaterLevel (bool splash = true);
 	native bool IsZeroDamage();
 	native void ClearInterpolation();
-	native Vector3 PosRelative(sector sec);
+	native Vector3 PosRelative(sector sec) const;
 		
 	native void HandleSpawnFlags();
 	native void ExplodeMissile(line lin = null, Actor target = null, bool onsky = false);
 	native void RestoreDamage();
-	native int SpawnHealth();
+	native int SpawnHealth() const;
 	native void SetDamage(int dmg);
-	native double Distance2D(Actor other);
-	native double Distance3D(Actor other);
+	native double Distance2D(Actor other) const;
+	native double Distance3D(Actor other) const;
 	native void SetOrigin(vector3 newpos, bool moving);
 	native void SetXYZ(vector3 newpos);
 	native Actor GetPointer(int aaptr);
@@ -511,7 +511,7 @@ class Actor : Thinker native
 	native void BloodSplatter (Vector3 pos, double hitangle, bool axe = false);
 	native bool HitWater (sector sec, Vector3 pos, bool checkabove = false, bool alert = true, bool force = false);
 	native void PlaySpawnSound(Actor missile);
-	native bool CountsAsKill();
+	native bool CountsAsKill() const;
 	
 	native bool Teleport(Vector3 pos, double angle, int flags);
 	native void TraceBleed(int damage, Actor missile);
@@ -559,21 +559,21 @@ class Actor : Thinker native
 	native void LinkToWorld(LinkContext ctx = null);
 	native void UnlinkFromWorld(out LinkContext ctx = null);
 	native bool CanSeek(Actor target);
-	native double AngleTo(Actor target, bool absolute = false);
+	native double AngleTo(Actor target, bool absolute = false) const;
 	native void AddZ(double zadd, bool moving = true);
 	native void SetZ(double z);
-	native vector2 Vec2To(Actor other);
-	native vector3 Vec3To(Actor other);
-	native vector3 Vec3Offset(double x, double y, double z, bool absolute = false);
-	native vector3 Vec3Angle(double length, double angle, double z = 0, bool absolute = false);
-	native vector2 Vec2Angle(double length, double angle, bool absolute = false);
-	native vector2 Vec2Offset(double x, double y, bool absolute = false);
-	native vector3 Vec2OffsetZ(double x, double y, double atz, bool absolute = false);
-	native void VelFromAngle(double speed = 0, double angle = 0);
-	native void Vel3DFromAngle(double speed, double angle, double pitch);
+	native vector2 Vec2To(Actor other) const;
+	native vector3 Vec3To(Actor other) const;
+	native vector3 Vec3Offset(double x, double y, double z, bool absolute = false) const;
+	native vector3 Vec3Angle(double length, double angle, double z = 0, bool absolute = false) const;
+	native vector2 Vec2Angle(double length, double angle, bool absolute = false) const;
+	native vector2 Vec2Offset(double x, double y, bool absolute = false) const;
+	native vector3 Vec2OffsetZ(double x, double y, double atz, bool absolute = false) const;
+	native void VelFromAngle(double speed = 0, double angle = 0) const;
+	native void Vel3DFromAngle(double speed, double angle, double pitch) const;
 	native void Thrust(double speed = 0, double angle = 0);
-	native bool isFriend(Actor other);
-	native bool isHostile(Actor other);
+	native bool isFriend(Actor other) const;
+	native bool isHostile(Actor other) const;
 	native void AdjustFloorClip();
 	native DropItem GetDropItems();
 	native void CopyFriendliness (Actor other, bool changeTarget, bool resetHealth = true);
@@ -588,8 +588,8 @@ class Actor : Thinker native
 	native void Howl();
 	native void DrawSplash (int count, double angle, int kind);
 	native void GiveSecret(bool printmsg = true, bool playsound = true);
-	native double GetCameraHeight();
-	native double GetGravity();
+	native double GetCameraHeight() const;
+	native double GetGravity() const;
 
 	native bool CheckClass(class<Actor> checkclass, int ptr_select = AAPTR_DEFAULT, bool match_superclass = false);
 	native void AddInventory(Inventory inv);
@@ -597,7 +597,7 @@ class Actor : Thinker native
 	native void ClearInventory();
 	native bool GiveInventory(class<Inventory> type, int amount, bool givecheat = false);
 	native bool TakeInventory(class<Inventory> itemclass, int amount, bool fromdecorate = false, bool notakeinfinite = false);
-	native Inventory FindInventory(class<Inventory> itemtype, bool subclass = false);
+	native Inventory FindInventory(class<Inventory> itemtype, bool subclass = false) const;
 	native Inventory GiveInventoryType(class<Inventory> itemtype);
 	native Inventory DropInventory (Inventory item, int amt = -1);
 	native bool UseInventory(Inventory item);
@@ -613,7 +613,7 @@ class Actor : Thinker native
 	native double GetDistance(bool checkz, int ptr = AAPTR_TARGET);
 	native double GetAngle(int flags, int ptr = AAPTR_TARGET);
 	native double GetZAt(double px = 0, double py = 0, double angle = 0, int flags = 0, int pick_pointer = AAPTR_DEFAULT);
-	native int GetSpawnHealth();
+	native int GetSpawnHealth() const;
 	native double GetCrouchFactor(int ptr = AAPTR_PLAYER1);
 	native double GetCVar(string cvar);
 	native int GetPlayerInput(int inputnum, int ptr = AAPTR_DEFAULT);
diff --git a/wadsrc/static/zscript/base.txt b/wadsrc/static/zscript/base.txt
index f5eda9022..a15b78de8 100644
--- a/wadsrc/static/zscript/base.txt
+++ b/wadsrc/static/zscript/base.txt
@@ -331,10 +331,10 @@ class Object native
 	native static uint MSTime();
 
 	native Name GetClassName();
-	native void Destroy();
+	native virtualscope void Destroy();
 
 	// This does not call into the native method of the same name to avoid problems with objects that get garbage collected late on shutdown.
-	virtual void OnDestroy() {}
+	virtual virtualscope void OnDestroy() {}
 }
 
 class BrokenLines : Object native
@@ -344,7 +344,7 @@ class BrokenLines : Object native
 	native String StringAt(int line);
 }
 
-class Thinker : Object native
+class Thinker : Object native play
 {
 	enum EStatnums
 	{
@@ -386,7 +386,6 @@ class Thinker : Object native
 
 class ThinkerIterator : Object native
 {
-
 	native static ThinkerIterator Create(class<Object> type = "Actor", int statnum=Thinker.MAX_STATNUM+1);
 	native Thinker Next(bool exact = false);
 	native void Reinit();
diff --git a/wadsrc/static/zscript/events.txt b/wadsrc/static/zscript/events.txt
index 24707055f..6452d19e0 100755
--- a/wadsrc/static/zscript/events.txt
+++ b/wadsrc/static/zscript/events.txt
@@ -1,6 +1,6 @@
 class BaseEvent native { } // just a base class. it doesn't inherit from Object on the scripting side so you can't call Destroy() on it and break everything.
 
-class RenderEvent : BaseEvent native
+class RenderEvent : BaseEvent native ui
 {
     native readonly Vector3 ViewPos;
     native readonly double ViewAngle;
@@ -10,7 +10,7 @@ class RenderEvent : BaseEvent native
     native readonly Actor Camera;
 }
 
-class WorldEvent : BaseEvent native
+class WorldEvent : BaseEvent native play
 {
     // for loaded/unloaded
     native readonly bool IsSaveGame;
@@ -28,7 +28,7 @@ class WorldEvent : BaseEvent native
     native readonly double DamageAngle;
 }
 
-class PlayerEvent : BaseEvent native
+class PlayerEvent : BaseEvent native play
 {
     // this is the player number that caused the event.
     // note: you can get player struct from this by using players[e.PlayerNumber]
@@ -37,7 +37,7 @@ class PlayerEvent : BaseEvent native
     native readonly bool IsReturn;
 }
 
-class UiEvent : BaseEvent native
+class UiEvent : BaseEvent native ui
 {
     // d_gui.h
     enum EGUIEvent
@@ -121,7 +121,7 @@ class UiEvent : BaseEvent native
     native readonly bool IsAlt;
 }
 
-class InputEvent : BaseEvent native
+class InputEvent : BaseEvent native play
 {
     enum EGenericEvent
     {
@@ -279,7 +279,7 @@ class ConsoleEvent : BaseEvent native
     native readonly int Args[3];
 }
 
-class StaticEventHandler : Object native
+class StaticEventHandler : Object native play
 {
     // static event handlers CAN register other static event handlers.
     // unlike EventHandler.Create that will not create them.
@@ -307,8 +307,8 @@ class StaticEventHandler : Object native
     virtual native void WorldTick(WorldEvent e);
 
     //
-    virtual native void RenderFrame(RenderEvent e);
-    virtual native void RenderOverlay(RenderEvent e);
+    virtual native ui void RenderFrame(RenderEvent e);
+    virtual native ui void RenderOverlay(RenderEvent e);
     
     //
     virtual native void PlayerEntered(PlayerEvent e);
@@ -317,11 +317,12 @@ class StaticEventHandler : Object native
     virtual native void PlayerDisconnected(PlayerEvent e);
     
     //
-    virtual native bool UiProcess(UiEvent e);
+    virtual native ui bool UiProcess(UiEvent e);
     virtual native bool InputProcess(InputEvent e);
     
     //
-    virtual native void ConsoleProcess(ConsoleEvent e);
+    virtual native ui void ConsoleProcess(ConsoleEvent e);
+    virtual native void NetworkProcess(ConsoleEvent e);
     
     // this value will be queried on Register() to decide the relative order of this handler to every other.
     // this is most useful in UI systems.
@@ -342,4 +343,6 @@ class EventHandler : StaticEventHandler native
 
     static native bool Register(StaticEventHandler handler);
     static native bool Unregister(StaticEventHandler handler);
+    
+    clearscope static native void SendNetworkEvent(String name, int arg1 = 0, int arg2 = 0, int arg3 = 0);
 }
diff --git a/wadsrc/static/zscript/inventory/inventory.txt b/wadsrc/static/zscript/inventory/inventory.txt
index cac9b9b8f..16a83c7a5 100644
--- a/wadsrc/static/zscript/inventory/inventory.txt
+++ b/wadsrc/static/zscript/inventory/inventory.txt
@@ -751,7 +751,7 @@ class Inventory : Actor native
 	virtual bool Use (bool pickup) { return false; }
 	virtual double GetSpeedFactor() { return 1; }
 	virtual bool GetNoTeleportFreeze() { return false; }
-	virtual void AlterWeaponSprite(VisStyle vis, in out int changed) {}
+	virtual ui void AlterWeaponSprite(VisStyle vis, in out int changed) {}
 	virtual void OwnerDied() {}
 	virtual Color GetBlend () { return 0; }
 
@@ -818,7 +818,7 @@ class Inventory : Actor native
 	//
 	//===========================================================================
 
-	virtual bool DrawPowerup(int x, int y) { return false; }
+	virtual ui bool DrawPowerup(int x, int y) { return false; }
 
 	//===========================================================================
 	//
diff --git a/wadsrc/static/zscript/inventory/powerups.txt b/wadsrc/static/zscript/inventory/powerups.txt
index 3b01c97b3..f6b14a051 100644
--- a/wadsrc/static/zscript/inventory/powerups.txt
+++ b/wadsrc/static/zscript/inventory/powerups.txt
@@ -285,7 +285,7 @@ class Powerup : Inventory
 	//
 	//===========================================================================
 
-	virtual bool isBlinking()
+	virtual bool isBlinking() const
 	{
 		return (EffectTics <= BLINKTHRESHOLD && (EffectTics & 8) && !bNoScreenBlink);
 	}
@@ -934,7 +934,7 @@ class PowerFlight : Powerup
 		+INVENTORY.HUBPOWER
 	}
 
-	bool HitCenterFrame;
+	ui bool HitCenterFrame;
 
 	//===========================================================================
 	//
diff --git a/wadsrc/static/zscript/mapdata.txt b/wadsrc/static/zscript/mapdata.txt
index 5a216ea5e..3d18f9f5e 100644
--- a/wadsrc/static/zscript/mapdata.txt
+++ b/wadsrc/static/zscript/mapdata.txt
@@ -1,5 +1,5 @@
 
-struct SectorPortal native
+struct SectorPortal native play
 {
 	enum EType
 	{
@@ -31,12 +31,12 @@ struct SectorPortal native
 };
 
 
-struct Vertex native
+struct Vertex native play
 {
 	native readonly Vector2 p;
 }
 
-struct Side native
+struct Side native play
 {
 	enum ETexpart
 	{
@@ -100,7 +100,7 @@ struct Side native
 	
 };
 
-struct Line native
+struct Line native play
 {
 	enum ELineFlags
 	{
@@ -143,7 +143,7 @@ struct Line native
 	native int						special;
 	native int						args[5];	// <--- hexen-style arguments (expanded to ZDoom's full width)
 	native double					alpha;		// <--- translucency (0=invisibile, FRACUNIT=opaque)
-	native Side						sidedef[2];
+	native readonly Side			sidedef[2];
 	native readonly double			bbox[4];	// bounding box, for the extent of the LineDef.
 	native readonly Sector			frontsector, backsector;
 	native int 						validcount;	// if == validcount, already checked
@@ -171,25 +171,25 @@ struct Line native
 	}
 }
 
-struct SecPlane native
+struct SecPlane native play
 {
 	native Vector3 Normal;
 	native double D;
 	native double negiC;
 	
-	native bool isSlope();
-	native int PointOnSide(Vector3 pos);
-	native double ZatPoint (Vector2 v);
-	native double ZatPointDist(Vector2 v, double dist);
-	native bool isEqual(Secplane other);
+	native bool isSlope() const;
+	native int PointOnSide(Vector3 pos) const;
+	native double ZatPoint (Vector2 v) const;
+	native double ZatPointDist(Vector2 v, double dist) const;
+	native bool isEqual(Secplane other) const;
 	native void ChangeHeight(double hdiff);
-	native double GetChangedHeight(double hdiff);
+	native double GetChangedHeight(double hdiff) const;
 	native double HeightDiff(double oldd, double newd = 0.0);
-	native double PointToDist(Vector2 xy, double z);
+	native double PointToDist(Vector2 xy, double z) const;
 }
 
 // This encapsulates all info Doom's original 'special' field contained - for saving and transferring.
-struct SecSpecial
+struct SecSpecial play
 {
 	Name damagetype;
 	int damageamount;
@@ -199,7 +199,7 @@ struct SecSpecial
 	int Flags;
 }
 
-struct Sector native
+struct Sector native play
 {
 	//secplane_t	floorplane, ceilingplane;	// defined internally
 	//FDynamicColormap *ColorMap;
diff --git a/wadsrc/static/zscript/menu/menu.txt b/wadsrc/static/zscript/menu/menu.txt
index 9f59b3239..81727ad2b 100644
--- a/wadsrc/static/zscript/menu/menu.txt
+++ b/wadsrc/static/zscript/menu/menu.txt
@@ -48,7 +48,7 @@ struct JoystickConfig native
 	
 }
 
-class Menu : Object native
+class Menu : Object native ui
 {
 	enum EMenuKey
 	{
@@ -287,7 +287,7 @@ class Menu : Object native
 
 }
 
-class MenuDescriptor : Object native
+class MenuDescriptor : Object native ui
 {
 	native Name mMenuName;
 	native String mNetgameMessage;
diff --git a/wadsrc/static/zscript/menu/menuitembase.txt b/wadsrc/static/zscript/menu/menuitembase.txt
index 35663d8b2..9b758c117 100644
--- a/wadsrc/static/zscript/menu/menuitembase.txt
+++ b/wadsrc/static/zscript/menu/menuitembase.txt
@@ -4,7 +4,7 @@
 //
 //=============================================================================
 
-class MenuItemBase : Object native
+class MenuItemBase : Object native ui
 {
 	protected native double mXpos, mYpos;
 	protected native Name mAction;
diff --git a/wadsrc/static/zscript/shared/player.txt b/wadsrc/static/zscript/shared/player.txt
index e8e022ef3..3821ff002 100644
--- a/wadsrc/static/zscript/shared/player.txt
+++ b/wadsrc/static/zscript/shared/player.txt
@@ -150,7 +150,7 @@ class PlayerPawn : Actor native
 	}
 	
 	// This is for SBARINFO.
-	int, int GetEffectTicsForItem(class<Inventory> item)
+	int, int GetEffectTicsForItem(class<Inventory> item) const 
 	{
 		let pg = (class<PowerupGiver>)(item);
 		if (pg != null)
@@ -167,10 +167,10 @@ class PlayerPawn : Actor native
 		return -1, -1;
 	}
 
-	native int GetMaxHealth(bool withupgrades = false);
+	native int GetMaxHealth(bool withupgrades = false) const;
 	native bool ResetAirSupply (bool playgasp = false);
 	native void CheckWeaponSwitch(class<Inventory> item);
-	native static String GetPrintableDisplayName(Class<Actor> cls);
+	native clearscope static String GetPrintableDisplayName(Class<Actor> cls);
 
 }
 
@@ -192,7 +192,7 @@ class PlayerChunk : PlayerPawn
 	}
 }
 
-class PSprite : Object native
+class PSprite : Object native play
 {
 	enum PSPLayers
 	{
@@ -239,7 +239,7 @@ enum EPlayerState
 	PST_GONE	// Player has left the game
 }
 
-struct PlayerInfo native	// this is what internally is known as player_t
+struct PlayerInfo native play	// this is what internally is known as player_t
 {
 	// technically engine constants but the only part of the playsim using them is the player.
 	const NOFIXEDCOLORMAP = -1;
@@ -340,22 +340,22 @@ usercmd_t	original_cmd;
 	native void PoisonDamage(Actor source, int damage, bool playPainSound);
 	native void SetPsprite(int id, State stat, bool pending = false);
 	native void SetSafeFlash(Weapon weap, State flashstate, int index);
-	native PSprite GetPSprite(int id);
-	native PSprite FindPSprite(int id);
+	native PSprite GetPSprite(int id) const;
+	native PSprite FindPSprite(int id) const;
 	native void SetLogNumber (int text);
 	native void SetLogText (String text);
 	native void DropWeapon();
 	native void BringUpWeapon();
 
-	native String GetUserName();
-	native Color GetColor();
-	native int GetColorSet();
-	native int GetPlayerClassNum();
-	native int GetSkin();
-	native bool GetNeverSwitch();
-	native int GetGender();
-	native int GetTeam();
-	native float GetAutoaim();
+	native String GetUserName() const;
+	native Color GetColor() const;
+	native int GetColorSet() const;
+	native int GetPlayerClassNum() const;
+	native int GetSkin() const;
+	native bool GetNeverSwitch() const;
+	native int GetGender() const;
+	native int GetTeam() const;
+	native float GetAutoaim() const;
 	native void SetFOV(float fov);
 }