That was awesome, I'm in love with the concept!
That gets a 4/5, though it is a 5/5 idea. I think for a future version or a sequal (if you intend to do one) I would say upgrades and, of course, better graphics, but as is this is a fabulous game. I love the boss fights, and the music all blends beautifully. This is original, awesome, and fun. Good job. Hell, great job!