The demo is pretty good! I'll admit that it's not perfect, but I liked it.
The controls feel okay, although there were some places that made me have to use all of the jump to reach which felt weird.
But the one thing that this demo shines at are the puzzles, funnily enough.
I know this will sound biased (and I guess it kinda' is) but this is no joke the first time in a puzzle game where I feel rewarded for beating a puzzle.
Most puzzle games I play usually make me feel like I finally can get the hell along when I finish a puzzle, because of how abstract the puzzle laws are.
But this game is pretty genius! Because it's based off of physics and magnets, I can understand that, I can understand how these objects work instantly, it's just about figuring out how they work together, and it made me feel super rewarded for beating it.
I got all 7 keys and I feel like Einstein.
Maybe just make some of the places where you jump slightly lower, because as a game developer, I wouldn't worry, but as a gamer, I think I would get irritated.
Cool experience!