Coming up with a good concept for a puzzle game is one thing, but actually designing different levels is a real challenge. Too easy, the game feels boring. Too hard, it becomes frustrating. I think this game has just the right balance in difficulty. Great job!
You might make a few mistakes before solving the puzzle, and sometimes confusing—but with a bit of observation, you figure it out. There were moments when the solution was right in front of me, and I thought, “What the heck am I doing?” (Yeah, I keep pushing that block on level 11 forward.)
The visuals and music are also well done. I especially love the moment when the music coincidentally matches the timing of switching planes.