I just played it for about 10 minutes and it works really well. It's fluid, responsive and fun. Is there any way to win or lose right now?
The sprites are quite nice as well. You might consider adding a few subtle shadows (the ambient occlusion kind of passive obfuscation, if you know what I mean) for yarn balls next to the wood (at the sides, top and bottom) to add a bit more plasticity to the scene. Also, the cats on top have got their shadows above themselves instead of below, which looks a little strange.
One more thing about the gameplay though, it's somewhat difficult to move a ball diagonally. I didn't even know this was possible at first and found out by accident. Sometimes I need more than 5 tries until the game finally recognizes my intention. Apart from that - very nice and motivating. It's cool to trigger those occasional "chain reactions".