Gorgeous animation and art style. :) Echoing other comments, I would suggest adding checkpoints and maybe increasing the number of lives starting out as well. Difficulty-wise it's still acceptable for me (similar to Cuphead, it's possible to progress with repeated attempts).
On the technical side, the game hung very badly upon loading and crashed. It was only playable for me on Steam, but I still experienced some lag upon startup and during gameplay. This is a very cute, fun game that has a lot of potential. I would be happy to replay if the overall experience was smoother.