! Intrigue: a Chess Variant
_Intrigue_ is a Chess variant with an extra psychological challenge. The King is in hiding, and one of the pawns knows where -- but which one?
+ The Rules
* At the beginning of the game each player writes the name of a square (e.g. E1, F8, B3) on a piece of card, and places it face-down in clear view, so it cannot be seen or changed. This square is the location where that player's King is hiding. The King starts the game beside the board, and its starting square is empty.
* One pawn from each side is marked underneath so that it can be recognised when captured, but not before. This pawn knows the location of the King, and is called the _Informant_. It may be placed in any normal pawn's position at the start of the game, and behaves no differently to any other.
* If a player captures a pawn, and before their next move, checks the base and finds the mark, then their opponent must surrender the card stating the location of their King. The King then returns to that square and any piece there is taken.
* The King may be voluntarily revealed in place of a player's normal move. They turn over the card stating the King's location: their King then appears as described. A King may not be voluntarily revealed on top of or adjacent to the opposing King, that may only occur through an informant's capture.
+ Special Cases
* If any pawn reaches the opposing end of the board, and is removed and replaced with a higher ranked piece, it may not be inspected, but is retained by its owner. If this pawn is the Informant, then the King is now safe, though this will not be obvious. Stalemate may still result in a draw, and inability to move may still force a resignation.
* If one informant captures the other, it may be promoted to a regular pawn. Again, the king is now safe, but this will be obvious to the opponent.
* If a King appears on A4, A5, H4 or H5, and satisfies the general conditions of castling (neither piece can have moved, and the King must not be in, move into, or move through check) then it may do so.
* If a king it appears on top of the opposing King, it wins, unless it is in checkmate, in which case both players lose. If it lands adjacent to the opposing King, it has the opportunity to move and may take the King, unless that would leave it in check; if it can neither take the King nor move away, it is in checkmate and loses.
* The Queen may commence from the Kings square, or the game may be played with two queens.
* The King is 'atomic' (borrowing from Atomic Chess), so that when it returns it removes not only the piece occupying its square, but also every adjacent square.