Nice wee game! As others have pointed out, the UI isn't exactly the most polished thing, but I think it still provides all the fundamentals you really need for a 48 hour game jam. As for the mechanic, it's a clever idea; it could probably do with a bit more hand-holding at the start, to make sure what is actually possible is clear to the player (for the first few levels I focused only on moving tiles I wanted to bring together to get to the number, wheareas moving other tiles out of the way - and not caring what they add up to - is a powerful tool here). Nice job!
EDIT: I also forgot to thank you for giving the option to adjust the volume/mute. I really needed it at one point when trying to figure out one of the levels :P