Cheat mode:
Press [F1] or ~ during game play to display the console window. Then, enter one of the following codes to activate the corresponding cheat function.

Effect	Code
God mode	please god
All items	please giveall
Kill all enemies	please killall
Open all doors	please open
Flight mode	please fly
No clipping mode	please ghost
Invisibility	please invisible
Recover health	please refresh