Tiny bit of screen jitter was the biggest outright issue I could see.
Moving while aiming makes sense but would make puzzle design potentially harder so maybe a slow down instead of a complete stop.
Something that I think would be nice would be a door entry animation, it was a bit odd watching my character run straight past the door before transitioning.
Key animation is difficult to notice, hidden by geometry/too fast a transition. Obviously an audio chime would be nice as well for some added satisfaction.
The level select has some layering errors i.e. the magnet being thrown underneath the key monitor.
I personally found the character to be a little stiff to play around with, they aren't fun in a vacuum (more of a platformer problem than a puzzler problem)
Mostly critical, but I enjoyed the demo! You're doing great and you're awesome also.