Typing in LTUS during gameplay enables infinite lives, but pressing F8 to pause the game and then pressing F6 allows the player to press Fire to skip levels. It also allows the player to select any weapon with the F2 to F7 keys.
A hole was punched into the disk, which should result in an error. If this punch isn't present, the game freezes and refuses to load.
Should this check be removed, the game will load fine then, but with one catch. The player will be unable to get past Level 4 as one of the platforms needed to progress has its collision removed. Further levels have no terrain whatsoever, resulting in the player falling through the platforms. Not only this, but the damage the player deals is halved.