Nice simple concept, pretty good execution.
Pros: I really liked the sound and graphics, which were simple but effective at communicating the feel. Polish was pretty good. I felt this was a good length, short and sweet.
Cons: I felt that the lack of an option to rotate the pebbles was jarring. Especially since the pebbles could be permanently rotated as they fell if grabbed again, and there was no good way to reset them. I don't know why, but sometimes as I was dragging a pebble would just freeze in place and then get dropped, which was frustrating, possibly a problem with my computer lagging?