Select the "Video/Audio" option, then select "Advanced",
and check "Console" to enable the console window.
Press ~ during game play to display the console window,
then enter one of the following codes.
Note: The codes must be reactivated after each level.
God mode - god
Disable enemy AI - notarget
Restore health - health 100
Display console commands - eventlist
No clipping mode - noclip
All weapons - wuss
All weapons and items - give all
Spawn indicated tiem - spawn
Kill all of indicated enemy class - killclass
Invisibility - hide
Disable invisibility - show