This game is an absolute banger !
The gameplay is easy to pick-up & very nervous. Loved the visuals & effects. Sound design on point. Screen shakes, flashs & all you need for some good juice.
My only little feedback is I would have gone with a more nervous soundtrack to fit with the frenetic shooting going on. But that's more a matter of taste & this one also fit pretty well.
edit : Just realized now. It sounds like there's different soundtracks, right? That's awesome... you can disregard my previous feedback
edit 2 : I aced it... ^^ managed to get so overpowered that I could just sit in the middle & wait without doing anything. You should maybe consider adding a cap on the bonuses so that you cant really get overpowered. or maybe just a maximum level (maybe around 20) so that the game stay challenging.
I had a great time playing this one.
Great work ! :)