Great work! It's a fun concept and you have some pretty good artwork!
I did struggle a bit to beat the first non-tutorial level, and only managed to pass it because of a bug where the ball would keep some of its momentum from the last run after hitting 'R' for retry. I think with some extra polish on the physics and a bit more juice (sound effects mostly, and a bit faster paced without having to wait for the ball to fully go into sleep mode by itself for next steps), it could be a pretty good game :)