run:
	moveq #0,d0		; set all to zero

mouse:

	move.w #150,d1
	bsr waitraster		: wait for raster line in d1

	move.w #$0FF,$DFF180	; change bg color
	
	btst #6,$BFE001		; is lmb prssed
	bne mouse		; 0 = pressed

end:
	rts


waitVBI:
	move.l $DFF004,d0	; get vpos
	lsr.l #8,d0		; shift 8 to left
	and.l #$1FF,d0		; mask out the 9bits of vpos
	cmp.l #$138,d0		; are we at VBI
	bne waitVBI		; no -> wait
	rts

waitraster:			; expects line to wait for in d1.w
	move.l $DFF004,d0	; get vpos
	lsr.l #8,d0		; shift 8 to left
	and.l #$1FF,d0		; mask out the 9bits of vpos
	cmp.l d1,d0		; are we at the wanted line
	bne waitraster		; no -> wait
	rts