Man, there is so much I love about this game, so I'm just gonna rattle them off: The intro is beautiful, and reminds me of classic retro games, the soundtrack is really well done (with bonus points for the bassoon), the little reload animations are gold, the environmental destructibles are fun and well animated, and the enemies are really cool and unique. Unfortunately, I somehow fell into the void during the boss battle, but the fact that you guys have a fully fleshed-out boss is incredible for a jam game. Extremely well done. If I had to offer one critique, I would say that the aim system felt just a bit off. The gun's center seems to be at the hand, and when looks towards the aim point, the actual projectile fires a bit higher than the aim (pictured below - couldn't screenshot my mouse, so I drew it in). 
That was pretty minor though, and I got the hang of it quickly. Very well done to all of you, what a fantastic job.