Say pieces on a board, make each a pair with another piece. like...
|55|44|66| |44|66|55| so figure out how a piece can move. pick any piece, try to move it somewhere. when you move a piece you have to move it's pair at the same time. when you move to a piece it's pair has to move at the same time too. a piece always becomes a pair with the piece it moves to. no matter how many pairs, there's only one answer to how a piece can move. A common problem, I forget what it's called. There's only one answer for how any piece can move, another piece has to move where the piece left. No piece can move to where a piece moves from. No such thing as a free space, a piece always moves to another piece. A pair never moves to a pair. so try this... draw for each piece a line from one piece to another that connects each piece to move from the first piece until the last piece that goes back where it starts. see this as a machine diagram. move a piece then figure the machine diagram again.
