Beautiful art style, you have an awesome sense of vision for making a game and it really shows here! Your main mechanic is lots of fun, and works really well with you art style.
To give some feedback, I think it would be cool if the levels were slightly more than just combat arenas, like having blocks that require the cannon to blow up, or jump heights that require flight to access.
Overall, wonderful work and I really enjoyed it! Congrats on submitting and thanks for the game!