diff --git a/src/zscript/ast.cpp b/src/zscript/ast.cpp
index f80498738e..1f416f7ade 100644
--- a/src/zscript/ast.cpp
+++ b/src/zscript/ast.cpp
@@ -54,7 +54,12 @@ static const char *BuiltInTypeNames[] =
 	"vector3",
 	"vector4",
 	"name",
-	"usertype"
+	"color",
+	"state",
+	"sound",
+
+	"usertype",
+
 };
 
 class FLispString
@@ -767,6 +772,7 @@ static void PrintFuncParamDecl(FLispString &out, ZCC_TreeNode *node)
 	PrintNodes(out, dnode->Type);
 	out.AddName(dnode->Name);
 	out.AddHex(dnode->Flags);
+	PrintNodes(out, dnode->Default);
 	out.Close();
 }
 
diff --git a/src/zscript/zcc-parse.lemon b/src/zscript/zcc-parse.lemon
index 09fadedb49..1861463f90 100644
--- a/src/zscript/zcc-parse.lemon
+++ b/src/zscript/zcc-parse.lemon
@@ -188,6 +188,7 @@ 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) ACTION.					{ X.Flags = A.Flags | ZCC_Action; X.Replaces = A.Replaces; }
 class_flags(X) ::= class_flags(A) REPLACES dottable_id(B).	{ X.Flags = A.Flags; X.Replaces = B; }
 
 /*----- Dottable Identifier -----*/
@@ -585,6 +586,9 @@ type_name1(X) ::= DOUBLE(T).				{ X.Int = ZCC_Float64; X.SourceLoc = T.SourceLoc
 type_name1(X) ::= STRING(T).				{ X.Int = ZCC_String; X.SourceLoc = T.SourceLoc; }
 type_name1(X) ::= VECTOR(T) vector_size(A).	{ X.Int = A.Int; X.SourceLoc = T.SourceLoc; }
 type_name1(X) ::= NAME(T).					{ X.Int = ZCC_Name; X.SourceLoc = T.SourceLoc; }
+type_name1(X) ::= SOUND(T).					{ X.Int = ZCC_Sound; X.SourceLoc = T.SourceLoc; }
+type_name1(X) ::= STATE(T).					{ X.Int = ZCC_State; X.SourceLoc = T.SourceLoc; }
+type_name1(X) ::= COLOR(T).					{ X.Int = ZCC_Color; X.SourceLoc = T.SourceLoc; }
 
 type_name(X) ::= type_name1(A).
 {
@@ -841,6 +845,17 @@ func_params(X) ::= .	/* empty */			{ X = NULL; }
 func_params(X) ::= VOID.					{ X = NULL; }
 func_params(X) ::= func_param_list(X).
 
+func_params(X) ::= func_param_list(A) COMMA ELLIPSIS.
+{
+	NEW_AST_NODE(FuncParamDecl,parm,stat->sc->GetMessageLine());
+	parm->Type = nullptr;
+	parm->Name = NAME_None;
+	parm->Flags = 0;
+	parm->Default = nullptr;
+	X = A; /*X-overwrites-A*/ 
+	X->AppendSibling(parm);
+}
+
 func_param_list(X) ::= func_param(X).
 func_param_list(X) ::= func_param_list(A) COMMA func_param(B).	{ X = A; /*X-overwrites-A*/ X->AppendSibling(B); }
 
@@ -850,6 +865,17 @@ func_param(X) ::= func_param_flags(A) type(B) IDENTIFIER(C).
 	parm->Type = B;
 	parm->Name = C.Name();
 	parm->Flags = A.Int;
+	parm->Default = nullptr;
+	X = parm;
+}
+
+func_param(X) ::= func_param_flags(A) type(B) IDENTIFIER(C) EQ expr(D).
+{
+	NEW_AST_NODE(FuncParamDecl,parm,A.SourceLoc ? A.SourceLoc : B->SourceLoc);
+	parm->Type = B;
+	parm->Name = C.Name();
+	parm->Flags = A.Int;
+	parm->Default = D;
 	X = parm;
 }
 
diff --git a/src/zscript/zcc_parser.cpp b/src/zscript/zcc_parser.cpp
index ba08f91eff..ce2dc98e74 100644
--- a/src/zscript/zcc_parser.cpp
+++ b/src/zscript/zcc_parser.cpp
@@ -88,6 +88,7 @@ static void InitTokenMap()
 	TOKENDEF (TK_LtGtEq,		ZCC_LTGTEQ);
 	TOKENDEF (TK_Is,			ZCC_IS);
 	TOKENDEF (TK_DotDot,		ZCC_DOTDOT);
+	TOKENDEF (TK_Ellipsis,		ZCC_ELLIPSIS);
 	TOKENDEF ('|',				ZCC_OR);
 	TOKENDEF ('^',				ZCC_XOR);
 	TOKENDEF ('&',				ZCC_AND);
@@ -112,6 +113,7 @@ static void InitTokenMap()
 	TOKENDEF (TK_Class,			ZCC_CLASS);
 	TOKENDEF (TK_Abstract,		ZCC_ABSTRACT);
 	TOKENDEF (TK_Native,		ZCC_NATIVE);
+	TOKENDEF (TK_Action,		ZCC_ACTION);
 	TOKENDEF (TK_Replaces,		ZCC_REPLACES);
 	TOKENDEF (TK_Static,		ZCC_STATIC);
 	TOKENDEF (TK_Private,		ZCC_PRIVATE);
@@ -172,6 +174,9 @@ static void InitTokenMap()
 	TOKENDEF (TK_Loop,			ZCC_LOOP);
 	TOKENDEF (TK_Goto,			ZCC_GOTO);
 	TOKENDEF (TK_States,		ZCC_STATES);
+	TOKENDEF (TK_State,			ZCC_STATE);
+	TOKENDEF (TK_Color,			ZCC_COLOR);
+	TOKENDEF (TK_Sound,			ZCC_SOUND);
 
 	TOKENDEF (TK_Identifier,	ZCC_IDENTIFIER);
 	TOKENDEF (TK_StringConst,	ZCC_STRCONST);
diff --git a/src/zscript/zcc_parser.h b/src/zscript/zcc_parser.h
index 7500185f80..5d5c85827a 100644
--- a/src/zscript/zcc_parser.h
+++ b/src/zscript/zcc_parser.h
@@ -119,6 +119,11 @@ enum EZCCBuiltinType
 	ZCC_Vector3,
 	ZCC_Vector4,
 	ZCC_Name,
+
+	ZCC_Color,		// special types for ZDoom.
+	ZCC_State,
+	ZCC_Sound,
+
 	ZCC_UserType,
 
 	ZCC_NUM_BUILT_IN_TYPES
@@ -437,6 +442,7 @@ struct ZCC_LocalVarStmt : ZCC_Statement
 struct ZCC_FuncParamDecl : ZCC_TreeNode
 {
 	ZCC_Type *Type;
+	ZCC_Expression *Default;
 	ENamedName Name;
 	int Flags;
 };
diff --git a/wadsrc/static/zscript/constants.txt b/wadsrc/static/zscript/constants.txt
index 12604234dd..aa72ee8ec1 100644
--- a/wadsrc/static/zscript/constants.txt
+++ b/wadsrc/static/zscript/constants.txt
@@ -804,3 +804,18 @@ enum ERenderStyle
 	STYLE_AddStencil,
 	STYLE_AddShaded,
 };
+
+// Type definition for the implicit 'callingstate' parameter that gets passed to action functions.
+enum EStateType
+{
+	STATE_Actor,
+	STATE_Psprite,
+	STATE_StateChain,
+}
+
+struct FStateParamInfo
+{
+	state mCallingState;
+	EStateType mStateType;
+	int mPSPIndex;
+}