This turned out pretty well! The game looks really good, and controls well enough.
This is all coming from playing by myself, but standing still and shooting is a bit tedious when you're trying to clear waves coming out of a spawner.
Something else that caught me for a few moment was selecting a character. I use a keyboard, and I didn't realize that the numbers were corresponding with my keyboard to select my character. It might be worthwhile to unify the controls so that pressing up/down/left/right on a keyboard is equivalent to using the D-Pad that was shown on character portraits, and you can simultaneously de-clutter and show more of them.
Additionally, I may have missed it, but I feel like I picked up probably 8-10 small keys, but there was no indicator for holding them like the big one for the boss doors - what exactly were those for?