Sound test:
At the "Habit Soft" logo screen, press Up + A.
Language change:
At the title screen, hold Up and press Select to toggle between Japanese and English languages. All Japanese text fully translated in English mode.
Extra 10 continues:
At the title screen, hold Up and press A, A, A, A, release Up. Hold Down, press B, B, B, B. A sound confirm correct code entry. Then start a new game.
Stage select:
At the title screen, hold Up and press A, A, A, A, release Up. Hold Down, press B, B, B, release Down. Hold Left, press A, A, release Left. And finally, hold Right, press B, Start.
