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?

Awesome Game developed, I really loved it, Lots of feature missing, if you guys keep working on it this game has potential to be great. Check out my review of your game see, what you guys can do. Keep up the good work. 

Very very very fun! With a little bit of polish it could became a selling game!

I can definitely see the similarity to Gauntlet. Though the default controller bindings are a bit iffy - if you expect the player to move the camera as it seems you should bind fire to one of the shoulder or trigger buttons, so they don't have to shift their fingers from the right stick to shoot.

And I got overwhelmed fast - lasted even less long than on a Gauntlet arcade machine.

Great style. Should add escape and exit / close buttons / binds. Persistent world meant lots of respawn deaths as first room was full of enemies and most character seem to be unable to hit anything at different elevation.