What an original concept ! I got stuck for a long time because I didn't understand the rules properly, it is not obvious at the start that the blue part cannot enter the box, and that is what I was trying to do. But once the concept is clearly understood that is pretty fun to play, even though it is sometimes hard to control the magnets properly.
Just a suggestion, why not using a sphere instead of a box ? It would make controls a bit easier I think, it's the edges of the box that make it hard to control.