Start the game with the "-DEVMODE" command line parameter. Then while playing the game, press one of the following keys to activate the corresponding cheat function. *NOTE* All levels will also be unlocked.

Code	Effect
Decrease speed	-
Increase speed	=
Toggle invincibility	Backspace
Toggle first and third views	F1
Load current position	F10
Toggle extra information	F11
Advance to next checkpoint	F2
Warp to Spawn point	F3
Toggle no clipping	F4
Return to default speed	F5
Save current position	F9
999 ammunition	O
All weapons	P