While playing, type any of these codes and have a blast.

Code         Effect
IDDQD        Invulnerability
IDBEHOLDx    Gain temporary ability. x can be:
               I=invisibility	    R=radition suit
               S=berserk	    A=automap
               V=invulnerability    L=lightamps
IDKFA        Full health, ammo, weapons, armor and keys
IDFA         As above, but no keys
IDDT         While viewing map. 1x= all map 2x=more details
IDCHOPPERS   Gain chainsaw
IDCLEVxx     Warp to level 'xx'
IDMYPOS      Displays your position and bearing
IDMUSxx      Music select. 'xx' is the level who's song you want.
IDSPISPOPD   Walk through walls!