;r0 = VDP address
	;r1 = current color
	;r2 = color increment
	;r3 = target line
	;r4 = screen bottom
	;r5 = scratch
	;r6 = right edge
	;r7 = counter
	;r8 = secondary counter
	ldim 1, r0
	ldim 240, r4
	ldimh 0, r4
	;320 == $140
	ldim $40, r6
	ldimh 1, r6
top
	ldim 0, r1
	ldim 1, r2
	ldim 5, r3
	ldimh 1, r3
	ldim 32, r7
	ldim 0, r8
	
	ldim increments, r9
	ldimh increments, r9
	
waitfirst
	ini $C, r5
	cmp r5, r3
	bne waitfirst
	ldim -1, r3
	bra waithblank
	
linestart
	ld16 r9, r8, r2
waitline
	ini $C, r5
	cmp r5, r3
	bne waitline
	
waithblank
	ini $D, r5
	cmp r5, r6
	bgr waithblank
	
	outi 14, r0
	outi 14, r1
	add r2, r1, r1
	addi 1, r3
	
	addi -1, r7
	bne normal
	ldim 32, r7
	ldim 0, r1
	
	addi 2, r8
	
	
normal
	cmp r3, r4
	bcs top
	bra linestart
	
increments:
	dc.w $0001
	dc.w $0040
	dc.w $0800
	dc.w $0041
	dc.w $0840
	dc.w $0801
	dc.w $0841
	dc.w $0841