Hi, I think your game is fun and I love the art and everything. And here is my feedback for your game.
1. You need to fix the jump mechanic, feels like there is a delay when touching the ground then wanting to jump again.
2. The smashing-down animation needs to be improved more, the jump-start state has to be fast I think.
3. I think there is a little bug in the boss fight, if I died when during the boss spinning and then I respawn the boss is still spinning.
4. Probably better if the boss's dialogue is only shown one time at the first encounter.
5. There is a sudden music volume boosted up, that's a bit weird since there is nothing intense happened.
Keep up the good work and continue making it into a full game, I believe your game has the potential for success.