I love the art and atmosphere, and the gun play feels great. Its definitely satisfying to kill enemies and see the score text pop up.
I struggled with the ammo acquisition though. I think the issue is that in most games I have enough ammo most of the time and acquiring it is easy, but instead here there's additional friction to acquiring ammo. I think I spent the majority of the time waiting to get more ammo, more so than actually fighting, and when I'm immune to bullets gathering ammo there isn't any tension because I'm fully immune.
I never figured out why having too much ammo was bad, or why that should be a bad thing?
I like the idea of using blue/red to avoid bullets and fight blue/red enemies, but I wish the ammo acquisition was more streamlined so I could get back to the fun part more easily. I think it is a fun game, its just a bit too much friction for me at the moment.