Four coins lie on a table and form a square. Now you are allowed to jump with a coin over another one, in any direction, i.e. also diagonally or however. You always have to jump all the way to the other side, so that the distance between 'jumper coin' and 'jumped over coin' is the same before and after the jump.
Is it possible to form a larger square? If yes, how? If no, why not?