Nice concept ! That's a really solid game, with a nice core mechanic ! I really enjoyed the puzzles, and the graphics, even if they are simple, fits perfectly in the gameplay.
However, I don't really see the theme in your game... There is a line between the characters, but it doesn't do anything gameplay-wise. The two characters need to help each other, but that's not really a "linked together" mechanic in my opinion ^^'.
But don't get me wrong, the game itself is really good, polished and very well done ! Congratulations =) !