Good game, neat concept.
Over all, very good. One problem that makes it eaasy is that each subsequent level uses the same path as the previous level, so in essence, you need only set up the last paths from before, and figure out what the new path will be.
Tye the following:
+make each level have different paths (not nessecarrily random, as there would be less strategy involved).
+try make paths over lap, so that sometime you need to switch the same bridge multiple times to orchestrate the balls paths.
+Have the balls go at different speeds ^_^. Also, with the last two ideas in mind, it might be helpful to make each balla different colour.
+Add other features? I can't think of any, but it would be cool to see some other events happen to affect the game play.
Anywho, you did a great job. I rated 10 for violence because of the lack thereof, and 8 verall because despite how good this is (and it really is ^_^) I know you can do better, and I can't wait to see future improvements on your game.
~Manatee <3