Very fun fusion of a bullet hell and Hotline Miami, which is definitely wearing it's influences on it's sleeve. Gunplay was solid, and it applied the limitation well. I liked the concept of having two characters with different gameplay styles mixed together, which added enough variety to keep the gunplay interesting.
I did find myself having issues with the room visibility mechanics sometimes, especially when standing in a doorway and getting shot by enemies right in front of me but completely invisible because they're in the next room. The shotgun also broke the cardinal rule of shotguns (i.e. "If I shoot someone in the face with a shotgun they die"), which was annoying at times. Overall just a few little rough bits here and there (e.g. intro text re-appearing on restart), but nothing game breaking.
Loved the actual gunplay mechanics, which felt very natural to use. It was great fun shooting down a wall and proceeding to wreck someone's day. Also those board particles and splatter effects were fantastic!
Overall a great entry, well done!