I like the overall aesthetic design. The enemies and player were very unique, and the map and especially the lighting were very cool. The lighting made for fun surprise moments of hordes of enemies coming out of a darkened room. The zero-cooldown on attacks added a fun action button mash to combat.
My only real complaint is the lack of sound. Some background music and some noises for attacking, enemies aggroing, and so on would have been very nice.
Overall, fun game!
(Also, thanks to enemies walking through a wall in level 2, I found what I will assume is an easter egg of a very big observer. Whether it was intended or not, it was very fun to find.)