Not very fun and sort of difficult for me, but I really liked the concept. It's actually very original. I understand the "fun" is sort of in the difficulty or puzzle nature of the game, but it was still a bit difficult for me from the beginning to get my feet into it. Maybe consider starting out easier, or writing some "tips" or a "tutorial" type thing for the first level. It can be as simple as "signposts" that display the tips and stuff.
Maybe if there were some easier way to get the two characters lined up on top of each other besides having them both run into a wall or something to line up, that would be nice too.