The art and animations look amazing! I also was confused on what I'm supposed to do in the boss room since I couldn't attack and the room didn't have anything special in it. And with the controls I would also say less is more. The Dash and Slide could easily be combined. There wasn't any reason to do a normal dash when you are on the ground and I often forgot to hold the down button. Also I'm not sure if double jump was even needed since you had wall jumps too.