To receive all nine weapons, full life and proximity mines, press and hold 
the letters W, A, and X all at the same time. Note: 

Your score is set back to zero every time you use this code. You can
also gain access to individual cheats by typing C7 

LEVEL1 DIAGNOSTIC at the DOS prompt when you begin the game.
Then, during play, try these key combinations: 


BackspaceG: Toggles God mode on or off. 

BackspaceW: Warps between levels. 

BackspaceN: Lets you walk through walls.

BackspaceR: Puts a skull image in front of your character. 

BackspaceI: Increases your score.