For a 24 hour contest that's pretty good. Well thought, the slow incoming spikeballs so the player will panic for not knowing where they're coming from. The calculated jump height, the speed. I think you got into some things that not every game designer would for a 24 deadline... That's all I'm saying. Oh yeah, and well.. The art matches the game well enough. Pixel art is hardly a bad choice for a game. At least in my opinion.