I had a ton of fun with this game. It may have scratched a specific itch that I didn't know I had... I really enjoyed the abstract level design! I kind of miss the less "real" levels from older games like Doom, Wolfenstein 3D, Quake, etc.
The gameplay in general was fun, though I do have a few critiques. I wish there were more weapons (a rocket of some sort would be nice!) The two attacks were good, but after a point it did start to get a little repetitive. The controls were solid most of the time, but they were a little floaty and that really hurt during jumping sections. I got stuck in the stairway geometry a few times in Chapter 1 level 3. The end boss... I ultimately beat it by standing behind a pillar and holding down attack. It would have been nice if there was a more "Active" strategy that worked better. That said, beating the boss that way did once again trigger nostalgia for some of those old FPS games where I used to exploit the AI like that.
Overall I really enjoyed this one a lot. Great work!