Pompeii Chess is played on a board composed of three 3x3 boards linked by shared corner squares along an ascending diagonal. This gives the board a total of 25 squares, a common size for small chess variants. The initial board set-up is as follows:
The game follows FIDE rules, with these exceptions:
As in Shogi, captured enemy pieces are held in reserve by the capturing player. They can be re-inserted as a friendly piece on any empty square on a subsequent turn. A captured Pawn cannot be re-inserted directly onto a square where it promotes.
Pawns move one step orthogonally toward the enemy's home (north or east for White, south or west for Black). Pawns capture one step diagonally toward the enemy's home (northeast for White, southwest for Black). A Pawn can double step from any of the four squares occupied by friendly Pawns in the opening array. There is no en passant capturing.
The King castles with either the Rook or the Knight by moving to the square it occupies. The Rook/Knight moves one square inward.
The board in Pompeii Chess is taken from the non-CV game Pompeii, available at the Zillions of Games web site in the Free Downloads section..
An implementation of Pompeii Chess has been written for Zillions of Games.