This looks pretty neat. I definitely like the overall look of the graphics; the more detailed stone / rock textures, in particular, look nice! I think the foreground / background could fit in together better, though; they both look good on their own, but the level seems to "float" in the middle of the screen rather than exist within the background itself, if that makes sense.
The nature of the game (along with the puzzle design) allow for a lot of creativity in the puzzle solving. I think that's a really strong trait for any puzzle game. I did have a little bit of trouble with the controls, playing the web-based demo on a PC. It looks like the game doesn't immediately "obey" the mouse movement, possibly as a way of making sure that's what you really want to do. However, that means that when the mouse cursor reaches the row / column I want to move to, the stuff I'm dragging is a little "behind" and ends up one row / column short, sometimes. (This might all be just something on my end, or related to the PC/mouse-based setup.)
The game did seem pretty hard to me. I would have loved the option to stop the ball and move parts of the level around outside of real time. That'd probably conflict with half of the point of the game, though.