Type fifthdimension at the main menu, then press
one of the following keys during game play to activate the corresponding
cheat function.

Key
Disable active codes [F1]
Big paddle [F2]
Single gun [F3]
Double gun [F4]
Missile gun [F5]
Laser [F6]
Level skip [F7]
Suicide [F8]
Protective beam [F9]