Definitely a cute idea! It felt a bit shallow, if I'm being frank, but perhaps this just isn't a genre I dip my feet into so often. - don't take that too harshly, it didn't need to be anything bombastic, but if you want more than slow-ramp-up flow, then perhaps consider adding a few more possible options. Perhaps a ball type that sums numbers together (modulo for >10, etc.), or one that allows for diagonals, or one that you can even store for later on the side, allowing for a bit more reserved player choice.
The sound effects were really fitting and quite nice, and the clarity of the game was exactly as it needed to be - nice job there as well!
I had an odd issue when trying the HTML version (which I attempted before the downloaded version); it seemed as though there were some odd offset between my mouse and the cursor in-game. They didn't line up, so I'd have to drag my mouse high on the screen and outside of the bounding box just to hit stuff in the middle of the actual screen.
This does have places it can go, and I think it's a neat concept.
