There's an old debate on whether or not Doom is just a fancy ray caster game, that it's simply a beefed up version of the Wolfenstein 3D engine. True, however, this is what Doom may have looked like if it was built using only the original Wolfenstein 3D engine, in this case the Raycasting Game Maker engine has been used.
A Bull Demon bites down on you as you fend him off with a lousy standard issue pistol. You can also see the fireball thrown by a near-by Imp drawing close.