This game is bursting with soul. I had a lot of fun with all the weapons and platforming, felt like I was always getting better.
I think the game could use a big art pass however; the camera is really close, would be nice to have more view of the surroundings to see where you're going and plan enemy encounters, it becomes very run-and-gun right now. The ui is hard to navigate and read, you throw it all at the player immediately and the names for each shop menu are pretty opaque about what it does; "Paintery" for example. Of course you can open them and grok it decently fast, though I'm still not sure where my points/money was displayed.
I also couldn't scroll the weapons menu, or any menu for that matter.
I'm sure you've got a plan for all this though. The base gameplay is super fun. Reminded me of Risk of Rain a bit, but if cactus had made it.
I didn't get a chance to try the multiplayer so you may be putting more effort towards that.