Super cool game! I really enjoyed it, the difficulty curve felt reasonable , which I found isn't easy to do. Either way, I managed to beat the final boss and switch of all of the crossbows. The movement actually felt good. I wasn't slipping and sliding all over the place.
My only suggestion is that next time try using a tilemap, it'll allow you to build levels easier and it'll make sure there aren't any 'seems' between the tiles.
Other all, you made a super fun game! Congrats! :)