Cheatcodes:

Type in these codes in the console brought forth by the tilde key (~):

iwillsurvive -- God-Mode. 
raindropskeepfallinonmyhead -- More ammo. 
takeittothelimit -- Ammo reload. 
hitmewithyourbestshot -- Computer rocks. 
closetoyou -- You become invisible. 
letmego -- Now you can jump levels. 
sky -- Removes the clouds, and makes the game a little faster.