NOTE: This game can be played directly in Windows using a third-party source port (see the links section below).
Press the M-I-L keys together at the same time while playng to get full health and ammo.
To use the rest of the cheats you must enter debug mode by running the game like this at the commandline: spear -debugmode. Then when in the game, hold [Alt], [Shift] and [Backspace] at the same time. Then you can use any of the cheats below:
[Tab] + B: Border color
[Tab] + E: End level
[Tab] + G: Toggle God mode
[Tab] + H: Hit yourself (?)
[Tab] + I: Items and lots of points
[Tab] + N: No clipping (walk through walls)
Description by VGTips