The shareware version contains the entire first episode of the game, Knee-Deep in the Dead.
NOTE: This game has a native Windows version but it is recommended to use a third-party source port (see the links section below).
Type in these codes one letter at a time during the game to cheat:
IDBEHOLD then A gives you the area map
IDBEHOLD then I makes you invisible
IDBEHOLD then L gives you the nightvision goggles
IDBEHOLD then R gives you radiation suit
IDBEHOLD then S turns on berserker
IDBEHOLD then V makes you invincible
IDCHOPPERS gives you the Chainsaw!
IDCLEV##: level warp (first # is episode 1-3, second # is level 1-9)
IDDQD: toggle God mode
IDDT: shows entire map (type while in map view), type again to show monsters/items, a third time goes back to normal
IDKFA: gives you all weapons, keys and ammo
IDMYPOS: gives your coordinates (x,y)
IDSPISPOPD: turns clipping off (walk through walls)
Description by VGTips