Such nicely put together game! I think the gameplay has a lot of potential, but I got to admit I got stuck (like a ...). I got very frustrated actually :( I wish I could undo a single stone or some more leeway to make mistakes and correct. I got into a loop where I figured out the path I want, but it's easy to put a stone a little too high or in the way and - especially is it happens at the beginning - that leads me to instantly restart and keep on building tension and frustration with failing to drop the stone at the right place a little more ahead.
I did like the mechanic very much and it's obviously well put together, so I think with more time to tweak the level design, it'd be a game worth buying.
I found 2 little niggles: 1 where I restarting so furiously that the new level starts with a stone just out the pipe and 2: I think the crank was supposed to show the whole level, but it wasn't working. Nice idea, for discrete crank use, though!