Doom Codes -

Cheat mode:
Enter one of the following codes during game play to activate the corresponding cheat function.

Effect	Code
Invincibility	iddqd
All weapons, keys, ammo, and 200% armor	idkfa
Berserker strength	idbeholds
Temporary invincibility	idbeholdv
Temporary invisibility	idbeholdi
Full automap	idbeholda
Anti-radiation suit	idbeholdr
Light amplification visor	idbeholdl
Walk through walls	idspispopd or idclip
Chainsaw	idchoppers
Level select	idclev<episode number><map number>
Toggle full map; full map and objects; normal map	iddt
Display coordinates and heading	idmypos
Change music to indicated level	idmus<level number>

Hint: Using sounds to find monsters:
Listen for weird sounds, like somebody breathing very hard during the game. Those sounds are the brown monsters that throw fireballs. When the sounds stop, that means you have killed them all. However, there still may be normal enemies with guns and shotguns or pig monsters.

The snorting sounds in the game are coming from the pigs. Once the sounds stop, that means you have killed all the pigs.

Hint: Nightmare mode:
Cheat codes cannot be used in nightmare mode. It is just like the regular game, except the monsters are stronger and harder to kill. Enemies will keep appearing non-stop on each level -- you have to try and get to the end before more appear.

Glitch: Death on stairs:
Kill an enemy while he is on the side of the stairs. The enemy will die, but will be floating on the side of the stairs. If you kill an enemy at the top of the steps, the enemy should dead but fall down the steps.

Glitch: Living death:
Allow an enemy to kill you. Once you have a bloody face and you are on the ground, enable the "God mode" code. Your character will come alive again, but will not be able to change guns, move, or shoot.