Great game!
I feel like it could use a bit more polish regarding weapon usage. I didn't understand that ammo could only be picked up by equipping that weapon type, and the trial and error cycle to find the effective weapon was also a bit of a hassle.
I also feel like it could use a bit more juice on the shooting department. Also, relying on the mouse wheel for weapon changin makes the game impossible to play on laptops (as shocking as it may sound, not everyone has a mouse!)
A bit of background music would have been really nice too!