Bear in mind, my depth perception for 3d games is terrible, but here's my honest review.
Pros: Art style is really good, controls are snappy, environments are interesting
Cons: Magnet Punch is difficult to land sometimes. It feels like certain platforms are too high to reach even if you hold the D button. Some level elements are not well-placed.
I feel you really got something going on here, but the level design could use some work to make the game easier. Like a lot of reviews said, the game is only hard because the design is rough.
I'd increase the range of the magnet punch to hit things from a farther distance less precisely, and make it so that jumps are easier to make if you just hold the D button (Don't make a platform that you can just barely reach even if you hold the button down!)
Otherwise good job! It's difficult to put a game out there, but I hope this will help you improve the game in future builds.