Simple but an enjoyable experience. I challenged myself with avoiding all crystals as well, which took a while, but is achievable excluding some of the unavoidable ones. I would like to see WASD controls added, some music, checkpoints as stated below, maybe some 2D shadows and post effects like bloom, ball squish/bounce animations, maybe a particle system when hitting walls, etc. Overall well done, it's impressive you pumped out so many levels.