This was quite fun!
The character felt nice to control, the magnet felt nice to throw (although the half-second between holding E and having the character actually prep themself to throw took some getting used to), and the puzzles were well-designed. I have to say, though, being unable to move while aiming feels a bit off. I had more than one instance where I ended up in the wrong place and couldn't aim properly, and lack of movement made it so I had to throw the magnet at the floor and hope it didn't fall off an edge.
I don't know if this was your doing or if something broke, but I had zero sound during my entire playthrough. I checked my volume mixer and everything and still, total silence. (Using the Windows build, if that helps debug).
When the game started up, the window ended up so large that the bottom and right sides were cut off. I recognize this as something that might get fixed, though, if you add resolution settings to the system preferences menu, and playing in fullscreen had no issues.
The very last puzzle is funny. It took some thinking, trying several things, and gave me that "a-ha!" moment you wanted to achieve, for sure. It's just that I'm not even sure if my solution is the right one. I threw the magnet from the top level under the big minus block while it was being pulled up and next to the button that drops the weight, such that the magnet held up the block just above the button and stopped the button from being pressed. That's a clever solution, it's just that between the tiny gap I had to get the magnet in and the chance that the magnet could just end up on the button, forcing a restart, makes me think I found an alternate solution. Just felt that was worth pointing out.
I also think it might be a good idea to introduce the semisolid platforms before the first hub puzzle. I kinda got myself stuck trying to jump up to chase the magnet after it landed on not a slope, and was confused for a second.
Minus the potential sound issues, I luckily didn't run into any glitches. Then again, I wasn't trying anything super out-there, so I wasn't properly glitch-hunting. Still, though, intended player experience was super clean!
Overall, fun time! Can't wait to see where else this goes.
-- Epsilon
(Edit: forgot my "lack of movement while aiming" point)