Program for the 6502 processor to run a reaction game

lightgame.s

	.org $8000
	
reset:
	lda #$ff		; set all of A register of 6522 to output
	sta $6003
	
	lda #$7f		; set all but last pin of B register of 6522 to output
	sta $6002

	lda #$01		; initial value of output: 1 0 0 0 0 0 0
	sta $6000
	
	ldx #$00		; set X and Y registers to 0 because we're using them later
	ldy #$00
	
loop1:
	cmp #$40		; if at end of row, go the other direction
	beq loop2
	
	clc				; change the lit LED (going left, displayed as right)
	rol
	sta $6000
	
	ldy $6000		; check for button press
	cpy #$80
	bcc skip1
	clc
	jmp pressed1

skip1:
	jmp loop1
	
	
loop2:
	cmp #$01		; if at end of row, go the other direction
	beq loop1
	
	clc				; change the lit LED (going right, displayed as left)
	ror
	sta $6000
	
	ldy $6000		; check for button press
	cpy #$80
	bcc skip2
	clc
	jmp pressed2
	
skip2:
	jmp loop2
	
	
pressed1:
	ldy #$00		; wait a bit to make it obvious which led was picked
wait1:
	iny
	cpy #$18
	bcc wait1
	
	cmp #$08		; check if they got the middle LED
	clc
	bne notcorrect1
	
correct1:
	inx				; increment wins
	stx $6001
	
	tay				; exit if wins==15
	txa
	rol
	rol
	rol
	rol
	cmp #$f0
	bcc correct1_nobrk
	brk
correct1_nobrk:
	tya
	jmp skip1
	
notcorrect1:
	tay				; increment losses by temporarily moving A to Y and X to A so we can add #$10, then moving everything back
	txa
	clc
	adc #$10
	tax
	stx $6001
	tya
	
	cpx #$f0	; exit if losses==15
	bcc skip1
	lda #$77
	sta $6000
	brk
	
; this is all the same as the previous section of code, but for when it's moving right
; because I couldn't make subroutines work

pressed2:
	ldy #$00
wait2:
	iny
	cpy #$18
	bcc wait2
	
	cmp #$08
	clc
	bne notcorrect2

correct2:
	inx
	stx $6001
	
	tay
	txa
	rol
	rol
	rol
	rol
	cmp #$f0
	bcc correct2_nobrk
	brk
correct2_nobrk:
	tya
	jmp skip2
	
notcorrect2:
	tay
	txa
	clc
	adc #$10
	tax
	stx $6001
	tya
	
	cpx #$f0
	bcc skip2
	lda #$77
	sta $6000
	brk


	.org $fffc ; set starting address
	.word reset
	.word $0000