Rules Set the pieces up as in regular chess, but without the pawns.
The first and eight ranks are safe havens , i.e., no piece can be captured on these ranks. The object of the puzzle is to move the pieces such that all pieces of one color trade places with the pieces of those of the other color, but no piece may ever move to a square where it could be captured. Make alternately white and black moves. In the easier variant, one should just move all the pieces to the other side of the board without paying attention to the final ordering of these pieces. In a harder variant, the setup at the end should be the same as at the beginning with only colors reversed, e.g., there should be a white rook at a8, etc.