Dam! It's a really nice game. I really enjoyed how hard the last level was. Please do more levels. We all had a lot of fun.
One thing you could do: Make (certain) pipes reusable, but I don't know if that breaks the game. If so, maybe remove them after they have been used. You made a game that can be expanded very easily. Placeable walls that bounce the ball back, pipes that teleport the balls, are obvious candidates. I really would play this again if you add more levels ^^