Press ESC and type in 'glazed donut' to enable cheat codes.With cheats enabled, type in any one of these during the game:

Code Effect

F3 Go back one level
F4 Advance one level
ALT F12 Gain five lives
ALT 8 Unlimited bombs
ALT K "beach ball" power up
ALT I "Inviso" power up
ALT T "morph" power up
ALT B "cloak" power up
ALT F7 or F8 Change your characters looks
ALT S Toggle scrolling on/off