diff --git a/Platform/Apple/virtual/src/core/mem.s b/Platform/Apple/virtual/src/core/mem.s
index f132530a..3dbde012 100644
--- a/Platform/Apple/virtual/src/core/mem.s
+++ b/Platform/Apple/virtual/src/core/mem.s
@@ -375,13 +375,21 @@ fatalError: !zone
 	dey
 	bne .dash
 	+prStr : !text "FATAL ERROR: ",0
-.msg2	lda (pTmp),y
-	beq .msg3
+
+	ldx #$FF	; for asm str, max length
+	lda (pTmp),y	; first byte
+	bmi .msg	; 	if hi bit, it's a zero-terminated asm string
+	tax		; else it's the length byte of a PLASMA string
+	iny		; advance to first char
+.msg	lda (pTmp),y
+	beq .done
+	ora #$80	; set hi bit of PLASMA strings for cout
 	jsr cout
 	iny
-	bne .msg2
-.msg3:	jsr bell	; beep
-.inf: 	jmp .inf	; and loop forever
+	dex
+	bne .msg
+.done:	jsr bell
+.hang: 	jmp .hang	; loop forever
 
 ;------------------------------------------------------------------------------
 ; Normal entry point for ProDOS MLI calls. This patches the code at $BFBB.
@@ -739,6 +747,8 @@ heapAlloc: !zone
 	bcs .needgc
 +	sta heapTop
 	sty heapTop+1
+	ldx pTmp	; return ptr in X=lo/Y=hi
+	ldy pTmp+1
 	rts
 .needgc	jsr inlineFatal : !text "NeedCollect",0
 
@@ -797,7 +807,7 @@ memCheck: !zone
 .done	rts
 
 ; Verify the integrity of the heap
-heapCheck:
+heapCheck: !zone
 	lda #0
 	sta pTmp	; we'll use pTmp for scanning
 	lda heapStartPg
@@ -991,14 +1001,22 @@ gc2_sweep: !zone
 	bcc .outer		; if not, loop again
 	rts
 
-doGC: !zone
+heapCollect: !zone
 	lda nHeapBlks
 	bne +			; edge case: if nothing on heap, skip collection
 	rts
 +	jsr gc1_mark		; mark reachable blocks
 	jsr gc2_sweep		; sweep them into one place
 	jsr gc3_fix		; adjust all pointers
-	jmp heapClr		; and clear newly freed space
+	jsr heapClr		; and clear newly freed space
+	lda #0			; heap end lo always 0
+	sec
+	sbc heapTop		; calculate new free space
+	tax
+	lda heapEndPg		; hi byte too
+	sbc heapTop+1
+	tay			; free space to X=lo/Y=hi
+	rts
 
 } ; end of !pseodupc $800
 loMemEnd = *
diff --git a/Platform/Apple/virtual/src/include/mem.i b/Platform/Apple/virtual/src/include/mem.i
index 2bd3a12f..a8b9e38f 100644
--- a/Platform/Apple/virtual/src/include/mem.i
+++ b/Platform/Apple/virtual/src/include/mem.i
@@ -243,7 +243,7 @@ DEBUG_MEM = $1A
     ; Print out the currently allocated memory blocks and their states.
 
 ;------------------------------------------------------------------------------
-CHECK_MEM = $1E
+CHECK_MEM = $1B
     ; Input: None
     ;
     ; Output: None
@@ -251,15 +251,32 @@ CHECK_MEM = $1E
     ; Check that memory manager structures (and heap structures, if a heap
     ; has been set) are all intact.
         
+;------------------------------------------------------------------------------
+CHAIN_LOADER = $1E
+    ; Input: X-reg / Y-reg - pointer to loader (X=lo, Y=hi) to add to chain
+    ;
+    ; Output: None
+    ;
+    ; Add a loader to the chain just after this loader. The current next
+    ; loader (if there is one) will be passed to the new loader with another
+    ; CHAIN_LOADER command.
+    ;
+    ; The purpose of a loader chain is to insert faster devices between the
+    ; main/aux loader (fastest) and the disk loader (slowest). Note that the 
+    ; main mem and aux mem loaders are conceptually one; a chained loader will
+    ; always be inserted after them, not between them.
+        
 ;------------------------------------------------------------------------------
 FATAL_ERROR = $1F
-    ; Input:  X-reg(lo) / Y-reg(hi): message pointer
+    ; Input:  X-reg(lo) / Y-reg(hi): message pointer. Message can be:
+    ; (1) a zero-terminated, hi-bit ASCII string, (assembly style), or
+    ; (2) a length-prefixed, lo-bit ASCII string (PLASMA / ProDOS style)
     ;
     ; Output: Never returns
     ;
-    ; Switches to text mode, prints out the zero-terminated ASCII error message 
-    ; pointed to by the parameters, plus the call stack, and then halts the 
-    ; system (i.e. it waits forever, user has to press Reset).
+    ; Switches to text mode, prints out the error message pointed to by the 
+    ; parameters, plus the call stack, and then halts the system (i.e. it waits 
+    ; forever, user has to press Reset).
     ;
     ; This command halts and thus never returns.
 
@@ -336,21 +353,6 @@ HEAP_COLLECT = $23
     ; process. Therefore, HEAP_COLLECT should not be run during a
     ; START_LOAD..FINISH_LOAD sequence, nor when hi-res page 2 is being shown.
 
-;------------------------------------------------------------------------------
-CHAIN_LOADER = $30
-    ; Input: X-reg / Y-reg - pointer to loader (X=lo, Y=hi) to add to chain
-    ;
-    ; Output: None
-    ;
-    ; Add a loader to the chain just after this loader. The current next
-    ; loader (if there is one) will be passed to the new loader with another
-    ; CHAIN_LOADER command.
-    ;
-    ; The purpose of a loader chain is to insert faster devices between the
-    ; main/aux loader (fastest) and the disk loader (slowest). Note that the 
-    ; main mem and aux mem loaders are conceptually one; a chained loader will
-    ; always be inserted after them, not between them.
-        
 ;------------------------------------------------------------------------------
 ; Convenience for writing assembly routines in PLASMA source
 ; Macro param: number of parameters passed from PLASMA to the asm routine
diff --git a/Platform/Apple/virtual/src/plasma/gameloop.pla b/Platform/Apple/virtual/src/plasma/gameloop.pla
index 4fd4827d..36482f67 100644
--- a/Platform/Apple/virtual/src/plasma/gameloop.pla
+++ b/Platform/Apple/virtual/src/plasma/gameloop.pla
@@ -50,8 +50,13 @@ const FINISH_LOAD    = $17
 const FREE_MEMORY    = $18
 const CALC_FREE      = $19
 const DEBUG_MEM      = $1A
+const CHECK_MEM      = $1B
 const CHAIN_LOADER   = $1E
 const FATAL_ERROR    = $1F
+const HEAP_SET       = $20
+const HEAP_ADD_TYPE  = $21
+const HEAP_ALLOC     = $22
+const HEAP_COLLECT   = $23
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Other constants
@@ -72,29 +77,29 @@ predef setWindow2, initCmds
 // Global variables
 byte mapNum
 byte mapIs3D
+word mapNameHash = 0
 word totalMapWidth
 word totalMapHeight
-word pFont
-word pMap
-word cmdTbl[64]
-word triggerOriginX, triggerOriginY
-word triggerTbl
-byte redraw
-byte frameLoaded = 0
-byte textDrawn = FALSE
-byte needRender = FALSE
 
 word skyNum = 9
 word groundNum = 10
 byte portraitNum = 1
 
+word triggerOriginX, triggerOriginY
+word triggerTbl
+
+word cmdTbl[64]
+byte frameLoaded = 0
+byte textDrawn = FALSE
+byte needRender = FALSE
+
 // Queue setMap / teleport, since otherwise script might be replaced while executing
 byte q_mapIs3D
 byte q_mapNum = 0
 word q_x
 word q_y
 byte q_dir
-word mapNameHash = 0
+
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Definitions used by assembly code
@@ -601,38 +606,12 @@ asm rawDisplayStr
   bne -
 end
 
-///////////////////////////////////////////////////////////////////////////////////////////////////
-// Convert a PLASMA string (starts with length, lo-bit ascii) to an assembly string
-// (zero-terminated, hi-bit ascii).
-asm toAsmStr
-  lda evalStkL,x
-  sta pTmp
-  lda evalStkH,x
-  sta pTmp+1
-  ldy #0
-  lda (pTmp),y
-  beq +
-  sta tmp
-- iny
-  lda (pTmp),y
-  ora #$80
-  dey
-  sta (pTmp),y
-  iny
-  dec tmp
-  bne -
-  lda #0
-  sta (pTmp),y
-+ rts
-end
-
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // General methods
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Fatal error: print message and stop the system.
 def fatal(msg)
-  toAsmStr(msg)
   mmgr(FATAL_ERROR, msg)
 end
 
@@ -829,6 +808,9 @@ end
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Load code and data, set up everything to display a 3D map
 def initMap(x, y, dir)
+  word pFont
+  word pMap
+
   // Set up the command table
   initCmds()