Really good game, I played all the way through and enjoyed it. I don't have much critics, so I'm going to be super neat picky: it feels weird that your bullets don't come from in front of you but from your side (I mean, from the gun really). It is coherent but it makes it hard to shoot enemies coming straight at you when they're really close. The other thing is reloading: at the moment I need to take my finger away from the movement keys to press R, which means I won't be able to move to the right when I hit reload, which is not ideal when I only have 10 seconds per level. Space would work better I think.
Again, this was neat picking on my part, this game is great and I really enjoyed it, good job!