Unfortunatly, if you use these cheat codes, any chances of a high score are gone.
Extra Life:
Pause the game via Caps Lock, then type in 'extra' to get an exta life.
Become Invisible:
Pause the game, then type 'INVIS'
Entrap Enemies (in Bubbles):
Pause the game, then type 'CATCH'
Points Added to Score:
Pause the game, then type 'SCORE'
Choose Level:
Press "l" in main menu