Ghostrider Chess, an intriguing variant devised by Ralph Betza in 1978, has piqued my interest due to its suitability for a game server implementation. This captivating game is played on a traditional 8×8 chessboard, utilizing standard pieces, with the exception of the knights:
- In Ghostrider Chess, knights take on an intriguing twist as they become invisible, earning them the name “Ghostriders”. Whenever a Ghostrider is moved, this action is announced aloud, along with the occurrence of a check. However, the square to which the Ghostrider is moved is not revealed, unless a capture takes place.
- Pieces from either side are allowed to pass over squares occupied by Ghostriders, even enabling them to castle unhindered.
- A Ghostrider is captured in the same way as other men, and the owner must concede the capture.
- Players have the option to reveal the location of a Ghostrider at any moment, mainly to prevent the opponent from passing through that square. Ghostriders do not capture each other unless a player announces that they both occupy the same square.
- When a player is in check from a Ghostrider, they have the option to attempt capturing the Ghostrider. However, if the attempt fails, it results in an immediate loss for the attempting player.
What could such a game look like? Let’s conduct an example:
1. e4 Gc6 (Black moved a Ghostrider from b8 to c6. It isn’t visible to White, and Black must remember the current location, which is the reason why it’s more convenient to let the computer do the computing stuff.)
2. e5 Gxe5 (Black declares that the white pawn has been captured by a Ghostrider. Visually, the pawn is merely removed from the board, leaving no visible trace of the Ghostrider’s presence. However, White can now begin to deduce the Ghostrider’s potential location, as it is expected to remain on e5 as long as the other pieces continue to move.)
3. d4 Gf3+ (Black is obliged to declare a check. White can either move the king, or attempt to capture the Ghostrider. Indeed, dealing with this specific situation is relatively straightforward. However, for the sake of the hypothetical scenario, let’s assume that White makes another move.)
4. f4 (As we know, it is allowed to pass through a Ghostrider, so White can move the pawn from f2 to f4, while the Ghostrider hides on f3. However, the check wasn’t resolved by this move, so White automatically lost the game.) 0-1