I enjoyed this quite a lot. Unfortunately I died at the arena boss (should've went for the ammo upgrade...) but the journey getting there was quite fun. What I especially liked was that there were many ways to fight back against enemies, whether it be through melee, shooting, or just throwing stuff at them.
The only thing though that can maybe improve the experience is the pacing. I felt like there were times where the waves were going on for a bit too long, so maybe either you can reduce the enemies health or shorten the amount of levels. This might be a subjective thing though, and I think the game on it's own right now is still really fun and well-polished. Good job!