; Spin until power off
  game_loop:
    jsr play_music_engine
    jmp game_loop

  ; Play song data
  play_music_engine:
    ; If duration lower than 0 load next note and play it
	lda note_duration
	beq load_next_note
	; If not then lower duration
	lda current_tempo
	beq reset_tempo
	dec current_tempo
	rts

  load_next_note:
    inc note_pointer ; Increment note pointer
    ldx note_pointer ; load note pointer into X
	lda songdata1, X ; load note
	sta note
    inc note_pointer ; Increment note pointer again
    ldx note_pointer ; load note pointer into X
	lda songdata1, X ; load note duration
	sta note_duration
	; check for special opcodes
	lda note
	cmp #$FD
	beq handle_rest
	cmp #$FE
	beq handle_jump
	cmp #$FF
	beq handle_end
	; if not special opcode, now sound the note
    jsr lookup_note  ; jump to note lookup subroutine
	rts

  handle_rest:
	ldx note ; load note pointer into X
	lda #$00 ; load rest data
	sta $4002; play note
	lda #$00 ; load rest data
	sta $4003; play note
	rts ; go back to playing the note

  handle_jump:
	lda #$00
	sta note_pointer
	lda #$00
	sta current_tempo
	lda #$00
	sta note_duration
	ldx note_pointer ; load note pointer into X
	lda songdata1, X ; load tempo
	rts

  handle_end:
    lda #$01
	sta done_playing
	rts

  handle_done_playing:
    ldx note ; load note pointer into X
	lda #$00 ; load rest data
	sta $4002; play note
	lda #$00 ; load rest data
	sta $4003; play note
	lda #$FF
	sta note_duration
	rts

  lookup_note:
    ldx note ; load note pointer into X
	lda periodTableLo, X ; load actual note
	sta $4002; play note
	lda periodTableHi, X ; load actual note
	sta $4003; play note
	lda done_playing
	cmp #$01
	beq handle_done_playing
	rts ; go back to playing the note

  reset_tempo:
	lda tempo_duration
	sta current_tempo
	dec note_duration
	rts