I had a lovely few hours with this game! The art is simple but appealing and clear, the puzzles are varied, and the different areas in the game are all distinct both visually and mechanically.
I don't feel the game is too short, I think it's just the right length to explore its mechanics without getting tedious. That said, I think a level editor would be great for keeping a community around this game, as fan levels can do things that would be too overwhelming as normal levels.
I got a stuck on the last two puzzles, but in both cases, it turned out I'd just forgotten about a certain mechanic.