Great intro! I didn't see any game breaking bugs, as you can always just restart the level. I went to see the crushing effect when something fell on you and I was disappointed to see you just disappeared. Would love too see the robot just explode in to nuts and bolts or something like that.
I also thought as I was playing it would be more fun if the time to switch polar signs was almost instantaneous. It could promote levels where you are holding on to the magnet and have to constantly switch polarity while being in a long hallway of attractors.
Have you thought of the player having the ability to recall the magnet? It may add more depth for levels where you don't completely call it back, but have it attract to you through a wall and activating something. Idk.
Keep up the great work!