A very interesting premise!
I'm not sure if it's intentional or a bug, but in the first or second wave in the pit arena battle, the enemies are invisible. It took me a while of running around in circles, getting hit and wondering where I'm being attacked from, and then shooting randomly at the ground to realize that some of the mini chicken enemy things were not rendered until I had killed them. They still had their sound cues, but it was difficult to hear them over the battle music.
Aside from that, pretty stellar work. I'm interested in seeing where this goes.