Good idea that would benefit from small changes
Manipulating gears to force a path is a good idea. A few things about this game bothered me though. No instructions on which keys to use had me passing the first level by just clicking the mouse, and thinking that's all I had to do. Second level didn't work like that. With nothing to tell me to use specific keys, I just went for the arrows. Ok, they work, but why make the player guess? Just stick it on the menu.
But then at the end of every level, I have to use the mouse again to click continue, AND then to select the next level. This seems to interrupt the flow of game play and seems redundant. Keys or mouse please.
Some levels weren't really puzzles. Level 5 is like this. Just keep going around the square and it eventually solves itself. I get that beginning levels should be easy, but there is nothing else to do but go around in "circles".
The key controls were a bit awkward as well. If I wanted to go right, then up, I'd often zoom past the corner, then have to wait for the marker to creep back and slip around the corner. It might be useful to just have the marker stop at any junction and let the player choose which direction to go.
That said, the monotone color was fine. Matched the implied thoughtfulness of the game, but even with the one color, it might have been neat to see darker or lighter levels as well. The graphics were sometimes a bit pixelated. The music was well composed, but additional soothing soundtracks or a song with a longer track so you hear the repeat less, would be a good touch.
The last point I'd add is merely a professional look. On the level screen, you've used four different fonts. A bit of restraint and more organization of your information/options could add a more polished look.
Overall, the idea is nice. It just needs some refining :)