To activate any of these codes, press the following buttons during game play, not when the game is paused. Words confirming each cheat will appear at the top of the screen after each one is entered.

Extra Life: Square, Triangle, Circle, Square, Circle, X, Square, Triangle, Circle, Triangle, Triangle, X.
Full Shields: Triangle, Triangle, X, Square, Triangle, Circle, Triangle, X, Square, X, Triangle, X.
Negative Palette Effect: Square, Triangle, Circle, Square, Square, X, Circle, Triangle, Square, Circle, X, Triangle.
Psychedelic Palette Effect: Square, Triangle, Circle, [Circle], Square, Triangle, Square, X, Triangle, X, Square.
Cloaking: Triangle, Square, X, Circle, Square, X, Circle, Triangle, X, Square, X, Triangle.
Crazy Robots: Square, X, Square, X, Circle, Square, Circle, Square, Triangle, Circle, Circle, Square.
Turbo Mode: Press Square, Triangle, Circle, Square, Circle, X, Square, X, Circle, Triangle, Square, X.
All Keys: Press Square, X, Circle, Triangle, X, Triangle, Triangle, X, Triangle, X, Triangle, X
Full Level Access: Press Triangle, Square, Square, Triangle, Circle, Circle, Square, Square, Triangle, Circle, Square, Square.

When you start a new game, you can go to any level. "Mega-Wowie-Zowie:"

Press Triangle, Square, Circle, X, Triangle, Square, X, Triangle, Square, X, Circle, Square.
Get every weapon fully-stocked.

"More-Wowie-Zowie:" Press Triangle, X, Square, Square, Triangle, Circle, Circle, Square, Triangle, Square, Circle, X.
All the weapons fully-stocked, full level access, and ten lives.
Invincibility: Press Square, Triangle, Circle, Square, Square, Triangle, Circle, Circle, Square, Triangle, Square, X.