Additional difficulty levels
Repeated press Left at the difficulty selection screen to access the "Very Easy" setting or repeatedly press Right to access the "Very Hard" setting.

Fat legged aliens
Enter ICHEAT as a name. Then, press Left, A, Right, Down during game play.

Mutant alien
Enter ICHEAT as a name. Then, press C-Down, Up, Z(2), C-Right, Right during game play. Enabling this cheat while facing a harvester will transform turn that alien into a mutant.

Surreal graphics
Enter ICHEAT as a name. Then, press Down, Up, Right(3), A, Left during game play.

Weapons power-up
Enter ICHEAT as a name. Then, press Down, Up(2), Z(2), Left, Right during game play.

All weapons
Enter ICHEAT as a name. Then, press A, Right, C-Down, C-Right, C-Up, A, Left during game play.

Dancer
Enter "ICHEAT" as a name. Then while playing a game, press Down, Up, C-Up, Down, C-Right, C-Right.

Suffer mode
Enter "ICHEAT" as a name. Then while playing a game, press C-Down, Up, Z(2), C-Right(2). Repeat the code to disable it

Smart Bomb
Enter your name as ICHEAT, during the game press A, C-Up, C-Up, Up+Left to launch a smart bomb. The bomb will destroy all minor enemies, shield generators and processors on the screen.