I really wish I could beat it, but I kept encountering a bug where I hit some spikes and would respawn, but the key wouldn't ever come back. I didn't have it and it didn't appear in the level again.
Other than that, though, it's a really cool puzzle platformer. You did an amazing job of teaching the mechanics through the gameplay and I got far enough to hear the music ramp up one level, which was a nice surprise.
If I were to change anything about the design, I think it would be to remove a couple of levels and put their ideas into the remaining levels. The puzzles themselves are great and the order they appear in the levels works well, but I think they just need to be condensed a little more.