just got through this game. Fun concept, too few levels :D (not critism, just want to say MORE! :D)
anyway, other suggestions if you want to flesh this out further:
A) make seperate controls for each char, eg WASD for the blonde and IJKL for the red haired girl, and keep the [Tab] to switch them.
B) i can imagine a multiplayer could be fun too (but i think the previous addition already enables this)
C) for more levels of course more mechanics are needed (eg physical chain that cannot magically teleport through walls, buffs that increase chain length, simultaneous moves when the chain is stretched to the max, etc..)