I cant remember if it was D3 or the 'expansion pack' called Levels of the World, but there was one level that had a huge room that was totally pitch black and the only way to find the enemies was to fire and then look for where the shots came from. Totally awesome room especially in the begining when it was full of enemies.
I was never very good at playing it but my brother was amazing...first game that was fun just to watch someone else playing. My bro was so aggressive and smooth with the strafing it was like a dance. Turn, strafe, rotating while pinning the enemy to the wall and then flipping over and taking out two more.
although the repetition of "find the blue key card, find the yellow key card, find the red key card, etc got boring for me it was still a nice game.