This was awesome! I wish there was an option to lock the Y axis to keep it like the original Wolf3D, I think the original version forced that (never played it, just assuming from description) so it's a shame not to see it here as an option.
Apart from that however, it's got genuine fun to use weapons (I love throwing a grenade in a crowded room and leaving :D) and well designed enemies that are fun to fight (or terrifying, those mantis things that just flood the room with stars..)
And best of all, the level design is great, so much was accomplished with grid based single height levels. Completed it in one sitting, it felt just long enough to be satisfying.