Awesome
AMAZINGLY great use of physics! Really original! The lack of music was concerning at first, but that definitely did not hinder the game whatsoever. I think music could be a nice addition to a game like this, although I don't think you will lose any marks for not including any, should you make a new/updated version of the game.
Music aside, there are three suggestions I could give here to make this game feel perfect for me.
1. A limit on the ball size/density, with included sound cap and maybe a looped humming once the maximum size is reached.
2. More work on the visuals. The physics worked excellently and looked brilliant, but could be enhanced to much greater levels with attention payed to motion exaggeration; e.g. a motion tail on the ball or collision effects.
3. More levels! This is a VERY addictive game. I have no doubt you will continue to get high scored ratings on this game for a while to come, and more levels will only increase the attention this submission recieves.
Originality is definitely a high point in this game, and I can imagine it will be hard to upkeep; The levels (Should you make more) especially. But if you should manage to produce something better than this is any of the ways I have listed, I wouldn't be surprised if you had a front pager with 90% 5 star ratings.
Good work!