processor 6502
	seg program
	org $803

.start
	sta $c050	; set graphics
        sta $c052	; no mixed mode
	sta $c057	; set hires
        
        ldx #0
.loop   inc $2000,x	; increment hgr byte
        inx
        bne .loop
        lda .loop+2	; increment hi byte of instruction
        clc
        adc #1
        sta .loop+2	; self-modifying code
        cmp #$40
        bne .loop
        lda #$20	; reset to $2000
        sta .loop+2
	jmp .start