Cheat Mode
Press BACKSPACE then TAB while playing to use the codes:

Code - Result:

ammo - Full Ammo
fullmap - Full Map
kill - Kill All Monsters
chojin - God Mode
weapon - All Weapons
armor - 200 Armor
invisible - Invisibility
next - Skip Level
keys - Get All Keys
keys - All keys
kill - Kill all monsters
depth - Toggle horizon distance
reanimate - All monsters respawn
respawn (seconds) - Set respawn time
reverse - Reverse left and right sound channels
shadows (number) - Set upper shadow limit
go (level number) - Level select
kick (player number) - Disconnect player in multi-player mode
killp (player number) - Kill player in multi-player mode
nick - Show current name in multi-player mode
nick (new name) - Select new name in multi-player mode