Sound test
Hold [L] + [R] and press [Start] when
the text "Press Start" begins flashing at the title
screen.
Level select
Hold [X] + [Y], then press [A]x4, [B]x4,
[A], [B], [A], [B], [A], [B], [A],
[B] when the text "Press Start" begins flashing
at the title screen. Enter this code again on the level selection
screen to select a specific stage within that level. Alternatively,
hold [X] + [Y] and press [A], [B], [A]x4,
[B]x4, [A], [B], [A], [B], [A],
[B], [A], [B] at the title screen.