gameLoop:				; all RESET/POWER-ON/one-time code is above this.
    inc sleeping		; set "sleeping" variable to 1
waitNmiEnd:
    lda sleeping
    bne waitNmiEnd		; infinite loop until "sleeping" is 0 (set by NMI)
						; this ensures the game loop executes 1 per frame

    ; game code
    ldx $0204
    inx			; move a sprite y-pos by 1
    stx $0204

    jmp gameLoop		; done with 1 frame of game logic loop back to top and wait for next frame

nmi:				; at ANY MOMENT the PPU will literally *interrupt* any line of the game loop above
    pha
    tya
    pha
    txa
    pha			; push all registers on stack so we can pop them off later
			; this is important b/c the game loop could have been right in the middle of using them (potentially)

 ; NMI code here
    lda #$00
    sta $2003
    lda #$02
    sta $4014				; redraw sprite OAM
 ; End NMI code

    lda #$00
    sta sleeping		; set sleeping variable to 0 to tell game loop we did our draw updates during VBLANK

    pla
    tax
    pla
    tay
    pla		; pop/pull register values back

    rti		; return from interrupt aka go back to game loop