This is a superb execution of the theme! Jumping feels good and makes sense immediately after the first time you try it.
I love the enemy designs, they remind me a lot of Kirby's Adventure. The animations and pixel art here are also amazing. The artist is crazy talented.
I think the game was a little too hard from the beginning, which kept me from getting very far before giving up. Maybe I'm just tired, but the limitations of the one mechanic make it difficult to effectively avoid projectiles and attack enemies at the same time. I think it could be a really stellar arcade game with more fleshed out combat or movement.