Cute game. I appreciate the variation in rock formations.
Up until Level 13, the puzzle layouts are generally pretty constricted, which limits the number of potential options at any given moment. Many of them are also somewhat "linear" in construction, in the sense that once I'm past a certain section I can stop thinking about that section. Perhaps there has to be some amount of linearity, but I personally like puzzles that feel more open-ended and "global" in construction.
Walking onto a gate as it is changing state is inconsistent. Sometimes I can walk onto a gate as it is opening, sometimes I can't. Sometimes I can walk onto a gate as it is closing, sometimes I can't. In Levels 14 and 15, these edge cases showed up a lot, and I kept getting inconsistent behavior. This was pretty frustrating. I didn't finish Levels 13 and 15.
I often play games like this and I usually get an undo button and instant restarts. I did not find such a button. I realize it's a difficult system to implement, but it makes it way more likely for me to stick with a puzzle game. I gave up after making a lot of moves on Level 15 and then accidentally walking onto lava because I wasn't paying attention to all boards.
I vaguely recall playing a PuzzleScript game that also explores this same general mechanic, but I can't remember now what it was called. Maybe I just recall reading about this mechanic in the documentation.