Note: This is the Game Boy Color game, not to be confused with Asteroids for the classic Game Boy.
Enter "CHEATONX" as a password. Then while playing the game, press Select to display a cheat menu. Press Up or Down to select a level or Left or Right to select a zone. Press A for invincibility (001 will appear if done correctly).
Enter "QRTREATR" as a password.
Enter "PROJECTX" as a password.