some lovely art and some clever world design, like looping back to be back near the start with powers needed to then progress further.
As others have mentioned a bit more feedback would help especially on the boss fight in my opinion, as I really wasn't sure I was doing the boss damage (until the boss defeated sign came up), maybe you could add some hurt sound effects or flash the boss a different colour for half a second or something...
I really liked some of the little artistic touches like popping the healing balloon with your weapon, and the sword flourishes.
Feels like a great basis to make a more complete game on top of, but still a good job!