Replace the call to the Toolbox with a raw read of the mouse from ADB registers to try to minimize the cost of mouse polling in the game loop.

BuGS/game.s

@@ -208,6 +208,7 @@ nextWord anop
 startGame entry
 		stz gameRunning
 		stz numSegments
+		jsl initPlayer
 		jsl spiderInitGame
 		jsl levelInit
 		jmp levelStart

BuGS/gamePlayer.s

@@ -13,18 +13,103 @@
 gamePlayer start
 		using globalData
 
+PLAYER_TILES_HIGH	equ 7
+
+MOUSE_MAX_X		equ GAME_NUM_TILES_WIDE*TILE_PIXEL_WIDTH-TILE_PIXEL_WIDTH
+MOUSE_MAX_Y		equ GAME_NUM_TILES_TALL*TILE_PIXEL_HEIGHT-TILE_PIXEL_HEIGHT
+
+STARTING_MOUSE_X	equ GAME_NUM_TILES_WIDE*TILE_PIXEL_WIDTH/2
+STARTING_MOUSE_Y	equ MOUSE_MAX_Y
+		
+initPlayer entry
+		lda #STARTING_MOUSE_X
+		sta mouseX
+		lda #STARTING_MOUSE_Y
+		sta mouseY
+		rtl
+		
+
 updatePlayer entry
 		lda gameRunning
 		beq updatePlayer_gameRunning
 		rtl
 updatePlayer_gameRunning anop
+		ldx #0
+		ldy #0
+; This code for reading the mouse data is based on some code which John Brooks helpfully provided, although I did things
+; quite differently because I have different needs.  But this is about as low cost as can be made for reading the position
+; of the mouse.
+		short i,m
+		phb
+		lda #$e0
 		pha
-		pha
-		pha
-		~ReadMouse
-		pla
-		pla
-		pla
+		plb
+		lda MOUSE_STATUS
+		bpl updatePlayer_noMousePoll
+		and #2
+		bne updatePlayer_mouseYOnly
+		ldx MOUSE_DATA_REG
+updatePlayer_mouseYOnly anop
+		ldy MOUSE_DATA_REG
+updatePlayer_doneMousePoll anop
+		plb
+		long i,m
+		bra updatePlayer_handleDeltas
+
+updatePlayer_noMousePoll anop
+		plb
+		long i,m
+		jmp updatePlayer_skipDeltas
+		
+updatePlayer_handleDeltas anop
+; The X register has the deltaX
+		txa
+		bit #$40
+		bne updatePlayer_negX
+		and #$3f
+		clc
+		adc mouseX
+		cmp #MOUSE_MAX_X
+		blt updatePlayer_doneX
+		lda #MOUSE_MAX_X-1
+		bra updatePlayer_doneX
+updatePlayer_negX anop
+		ora #$ffc0
+		clc
+		adc mouseX
+		bpl updatePlayer_doneX
+		lda #0
+updatePlayer_doneX anop
+		sta mouseX
+		
+; The Y register has the deltaY
+		tya
+		bit #$40
+		bne updatePlayer_negY
+		and #$3f
+		clc
+		adc mouseY
+		cmp #MOUSE_MAX_Y
+		blt updatePlayer_doneY
+		lda #MOUSE_MAX_Y-1
+		bra updatePlayer_doneY
+updatePlayer_negY anop
+		ora #$ffc0
+		clc
+		adc mouseY
+		bpl updatePlayer_doneY
+		lda #0
+updatePlayer_doneY anop
+		sta mouseY
+
+; The Y register also has a bit in it which indicates whether the
+; mouse is down or not.
+		tya
+		and #$0080
+		sta mouseDown
+
+updatePlayer_skipDeltas anop
+		lda mouseX
 		lsr a
 		bcs updatePlayer_shift
 		adc #$9834
@@ -33,7 +118,7 @@ updatePlayer_gameRunning anop
 		bra updatePlayer_dirty
 		
 updatePlayer_shift anop
-		adc #$9834
+		adc #$9833
 		tay
 		jsl drawShipShift
 		bra updatePlayer_dirty
@@ -66,5 +151,9 @@ updatePlayer_dirty anop
 		sta tileDirty+1246
 		sta tileDirty+1248
 		rtl
-	
+
+mouseX		dc i2'0'
+mouseY 		dc i2'0'
+mouseDown   dc i2'0'
+
         end

BuGS/globals.s

@@ -142,6 +142,8 @@ NEW_VIDEO_REGISTER      gequ $e0c029
 BORDER_COLOUR_REGISTER  gequ $e0c034
 STATE_REGISTER          gequ $e1c068
 VERTICAL_COUNTER        gequ $e0c02e
+MOUSE_STATUS			gequ $c027
+MOUSE_DATA_REG			gequ $c024
 
 
 gameRunning	dc i2'1'

BuGS/main.c

@@ -62,8 +62,6 @@ int main(void)
     
     InitMouse(0);
     SetMouse(transparent);
-    ClampMouse(0, (GAME_NUM_TILES_WIDE - 1) * 8, 0, 8 * 5);
-    PosMouse(GAME_NUM_TILES_WIDE * 4, 8 * 5);
     
     initTiles();
     initNonGameTiles();

BuGS/tiles.h

@@ -126,7 +126,6 @@ extern word numInfieldMushrooms;
 /* API */
 
 extern void initTiles(void);
-extern void initPlayer(void);
 extern void addStartingMushrooms(void);