I absolutely love this game, the music is catchy, and the sound effects are perfect, you can really feel the weight of the ammunition! It's also helpful in the sense of knowing if you have a hard hitting gun or not >:D
I also love the variety of the weapons, theres a lot to experiment with which really adds to the replayability, overall the game is awesome.
The only constructive criticism I have is the visibility of the HUD, with how fast paced the game is, it can be hard to check on health & ammunition, this would probably be hugely helped by making the ammo number bigger/bolder, and the pink of the health bar more of a visible straight line. (The zig-zags are cool but it's hard to see out of the corner of my eye rip, maybe an additional solid straight line through the middle to preserve the design?)
All that aside though, I really really enjoyed this, you outdid yourself with this one :D