This has no right to be so addicting. :D
I'm not really a puzzle person, but something about circus music paired with hard challenges makes this such a blast. The levels do get really hard towards the end, but I guess that's the charm of it.
A small suggestion: I wondered if I could cheat the level by putting the grey boxes everywhere. I realized there was a limit to them. Would be good to have a counter for that somewhere in the UI.