Karen Robinson invented this chess-based puzzle, based on a puzzle from
the computer game `The 7th Guest' (a puzzle game with a horror theme),
which her son played.
Hans Bodlaender first named this game `Chess Squaredance', but it was renamed
later `Chess Contradance', as Karen Robinson remarked that the setup is more
like a contradance with the two lines facing each other.
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.
This puzzle may be quite hard. Email me how many moves you need in your
solution, and I'll publish the best attempts of both variations.
Written by Hans Bodlaender, based on email of Karen Robinson, who stated
`I don't know whether my variation is really original or not'.
WWW page created: November 6, 1998. Last modified: November 11, 1998.
Last modified: Sunday, April 1, 2012