I really like the artstyle and the fact you managed to make a working fps in such a short time frame is quite impressive in itself. Some things to note if you are planning to improve this after the jam - I would really like an enemy indicator ui op up when the enemy gets behind you, a lot of times I was oblivious about them and they just sneaked right up. After like wave 3-4, the game became quite boring to play, although that might be just me :P but I would really like some variations in the enemy type and maybe environment.
Overall, quite an impressive entry.