This is a bit sad really. But I am really seeing quite a lot of ways to make this game fun and exciting when done well! The core gameplay loop is surprisingly nice, it's simple and quick to the point where the brain is still wanting more each time the level is done. This has great potential for a highly addictive game in my mind. (Mind I steal the idea? XD JK)
I would say much criticism as I feel like a lot hasn't been realised yet, so it would be a bit unfair to judge it in the current stage, My only suggestion for this is to add a button (likely the down button) to trigger balls moving forward, so that I don't need to wait the few seconds after I've put down my buckets.
Anyway, keep up the good work!