This is intended to be a logical expansion of chess to a 10x10 board.
It adds two well known pieces, and a new one that is closely related.
The Pawn, King, Queen, Bishop, Knight, and Rook all have their familiar moves, including the pawn's initial double step and en passant.
The Gryphon makes a single diagonal step and then slides outward as a rook.
The Zebra jumps to the squares one diagonal step outward from those reachable by the Knight. It complements the Knight as the Gryphon complements the Rook.
The Osprey is a diagonal Gryphon. It jumps to the second square on the same rank or file, and then slides outward as a bishop. It complements the Bishop.
The rules are the same as chess, with the following exceptions.
A pawn may promote on either the 8th, 9th, or 10th rank. Promote on the 8th and 9th ranks is optional. The choice of which piece to promote to varies with each rank.
- Upon reaching the 8th rank, a pawn may promote to a Knight, Zebra, Bishop, or Osprey.
- Upon reaching the 9th rank, a pawn may promote to a Rook or Gryphon.
- Upon reaching the 10th rank, a pawn must promote to a Queen.
The King and Rook may castle. When castling, the King moves three squares towards the Rook, and the Rook moves to the last square passed over by the King. To castle, the following conditions must be met.
- Every square between the King and Rook must be vacant
- The King must not be in check
- None of squares between the King and Rook may be attacked by a hostile piece
- Neither the King nor Rook may have moved yet
This game originally only added the Gryphon and Osprey. It took longer for me to realize that the Zebra belonged too.
The promotion rules are intended to provide interesting options. I don't know how well they work.
I wasn't sure whether or not to allow castling, but I think it could be useful.
Expanded Chess can be played through Game Courier with this preset.
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By Daniel Zacharias.
Last revised by Daniel Zacharias.
Web page created: 2017-01-19. Web page last updated: 2020-04-21