Hey there, I've tried your game out and I thought it was quite clever. As I progressed it felt rewarding to figure out the puzzle even before pressing a key. The aesthetic and sound effects fit pretty well too.
1) Same as another commented above... I had to pick my hand up off the keyboard to click a mouse button to try again/reset and it started to become annoying.
2) The level design was interesting. I actually anticipated each level to progressively be more difficult especially after introducing a new mechanic. But I found a few that were unexpectedly easy, but it felt great to solve it quickly. Might be neat to reward the player for solving a level faster than usual, if there were a point system.
3) When moving the blocks off the edge, it would have been nice to have some sort of visual feedback that I was close to falling (maybe change the scale or change to a straight face or something?) Not ashamed to admit it took me a few tries to get the whole falling off thing and I was pretty close to quitting, but pressed on.
4) Seeing the Red Cube on the left side for so many levels, then for it to suddenly be on the right side was jarring. I almost wished the Red Cube flashed for a bit when the level loads just to get my bearings.
Excellent job, though! Really cool to see your game mechanic used in a variety of interesting ways