Load the game as usual and don't do anything until the high score screen appears. Type 'COMMANDER' and then press the fire button. After a few moments press F10. If your ship flickers you are now invulnerable and have infinite expansions and smart bombs. F1F5 Other Six Levels of 'expansion' you can still capture the capsules
F8 Advance a level There are three
F10 Turn cheat mode on/off
You cannot get a high score with the cheat mode on.