It's a very interesting idea (I love physics puzzles by the way), although I have to agree with Robin - it's a bit too fast paced and I don't really feel in control of the cannon ball. Maybe if it wasn't scrolling (at all or at least that much, so the level would more or less fit on the screen) and the falling was happening in slo-mo it would be a bit less about luck and more about the player rotating the magnets just the right way. The original idea is great and I can definitely see you building upon this and consequently making a wagon of cash porting the game to mobile and selling different looking cannon balls as in-app purchases! ;)