Rules

The Rules of Circular Chess
by Alan and Martin Mattlage

Introduction

Circular Chess is a game for two players, "White" and "Black." The players control the same number and kinds of pieces that are used in traditional Chess. All of the rules of Circular Chess are as like to traditional Chess as the board allows.

For players already familiar with Chess, the first section of this document provides a brief summary of the differences that arise due to the new board geometry. For players new to Chess, the remaining sections provide a complete explanation of all rules governing the play of Circular Chess.

There are three versions of the Circular Chessboard (see the discussion of boards in The Complete Rules section). This document, for the sake of simplicity, uses what is known as the "Medial" board for all illustrations. The rules, however, apply to all three versions.

For Experienced Chess Players

o The Board and Set Up

The Circular Chessboard should be placed between the two players so that the void spaces at the outer perimeter of the circle are the same distance from both players. During the course of a game, pieces are not permitted to occupy the center-circle or void spaces.

The starting positions of White's pieces are the same as in traditional Chess. The board must be oriented so that White's King Rook is located on a light-colored space to White's right. Unlike a square Chessboard, there is only one orientation of a Circular Chessboard that meets this requirement.

The starting positions of Black's pieces are placed in a mirror image of the arrangement used in traditional Chess with Black's King Rook located on a dark space to Black's right. This retains the feature of traditional Chess that places Black's Queen on the same file as White's Queen and Black's King on the same file as White's King. See figure 2 for an illustration of initial piece positions.

o Movement and Capture of Pieces

The movements of all pieces on the Circular Chessboard are analogous to their movements on a traditional Chessboard. For Rook-like movements, spaces that lie along circle diameters act as files while spaces that lie along complete circles and circular segments act as ranks. Arcs of same-color spaces that lie along inward and outward curving diagonals act as the diagonal paths along which Bishop-like movements are made.

When the movement path of a piece encounters the center-circle of the Circular Chessboard, movement continues across the center in the spirit of the movement made approaching the center. A Rook-like movement continues to the opposite-color space directly across the center. A Bishop-like movement curving left continues to the same-color space just to the left of the space directly across the center and then onward to the left. Movements of Kings, Knights, and Pawns that cross the center-circle can be easily determined if the player keeps in mind that spaces directly across the center-circle from one another are considered adjacent spaces that are in the same file. The center-circle is not considered a space and it cannot be occupied by a piece. See figures 3 through 13 for examples of piece movements.

While pieces are permitted to pass through the center-circle, they may NOT move across void spaces. This applies to Knights as well as all other pieces.

A Rook or Queen may not make a move that returns it to the space from which it started.

In Circular Chess, all pieces capture in the same manner as in traditional Chess while observing the movement differences described in the previous paragraphs.

o Pawn Promotion

Just as in traditional Chess, when a Pawn reaches its opponent's first rank, it may be promoted to another piece of higher value. In Circular Chess it is possible for a Pawn to reach its OWN first rank. Depending on its starting position and the number and direction of captures it makes during the course of a game, it may end up moving "forward" toward its own side of the board. In this case, the Pawn may also be promoted.

The Complete Rules of Circular Chess

o Objective of the Game

The objective of Circular Chess is to position your pieces so as to checkmate your opponent's King.

o The Board

The Board is circular and divided into seventy, sixty-eight, or sixty-six spaces, depending upon whether the version that is being played is "Maximal," "Medial," or "Minimal" Circular Chess. Spaces are alternately colored dark and light. The three versions of the board are shown in Figure 1.

The centers of these boards are not part of the playing field of the game. The centers have been removed in order to avoid the visual confusion resulting from the board's converging files. Throughout this document this center area will be referred to as the "center-circle". Void spaces on the left and right of each board are also not part of the playing field and will be referred to simply as "void spaces." The center-circle and void spaces are fundamentally different with respect to piece movement.

Rows of playing field spaces that are aligned along circle diameters will be referred to as files, while rows of spaces that lie along circles or circle segments will be referred to as ranks. For referring to individual spaces, a system known as algebraic notation has been adapted from traditional Chess to identify each space on the Circular Chessboard. The files, starting with White's left-most, full-diameter file and proceeding counterclockwise up to and including the file containing void spaces, are assigned the letters "a" through "i". The ranks, starting with White's first rank and proceeding across the center and continuing to Black's first rank, are assigned the numbers "1" through "8". Using this convention, an individual space on the board can then be located using its file and rank designations. For example, the space just to the right of the void spaces on White's left is "i6" on a Medial style board.

o Set Up

The board should be placed between the players as shown in Figure 2. The right-most space in White's first rank should be light-colored.

Each player controls a set of pieces consisting of two Rooks, two Knights, two Bishops, one Queen, and one King. White's pieces are placed on the spaces in White's first rank (rank "1"), while Black's pieces are placed on the spaces in Black's first rank (rank "8"). Each Rook is placed adjacent to a void space, Knights are placed adjacent to Rooks, and Bishops are placed adjacent to Knights. White's Queen is placed on the vacant, light-colored space, and White's King is placed on the vacant, dark-colored space. Black's Queen is placed on the vacant, dark-colored space, and Black's King is placed on the vacant, light-colored space.

Each player also controls eight Pawns. White's Pawns are placed on the spaces in White's second rank (rank "2"). Black's Pawns are placed on the spaces in Black's second rank (rank "7").

See Figure 2 for an illustration of the initial positions of all pieces and Pawns.

o Movement and Capture of Pieces

Before the start of the game, players must decide by mutual agreement or by some random method who will be White and who will be Black. White always makes the first move. White and Black then take turns making moves, making one move per turn. A move must consist of repositioning one of a players own pieces (or in the case of Castling, two pieces) or capturing an opponent's piece. While in play, no two pieces may occupy the same space simultaneously, nor may they ever occupy the center-circle or a void space.

The same etiquette with regard to touching and moving pieces applies to Circular Chess as in traditional Chess. That is: Once a piece has been touched, it must be moved if it has a legal move. And once a piece has been moved to a space constituting a legal move or capture and has been released, the move is complete and cannot be taken back.

+ The Rook

The Rook may move to any space on the file it occupies, as long as there are no pieces between it and its destination. It may also move to any space on the rank it occupies, as long as there are no pieces or void spaces between it and its destination.

The Rook may capture an opposing piece if the opposing piece occupies a space that constitutes a legal destination within the Rook's range of movement. To capture, the Rook is placed in the destination space and the opposing piece occupying the space is removed from the board.

While the Rook is permitted to pass through the center-circle, it may NOT move across void spaces. Also, the Rook may not occupy the center-circle or void spaces.

A Rook may not make a move that returns it to the space from which it started.

A Rook may not make a move or capture that places its own King in check.

See Figure 3 for an example of spaces to which a Rook might move.

+ The Bishop

The Bishop moves similarly to the Rook except in a "diagonal" manner rather than a "file and rank" manner. To visualize a "diagonal" on the Circular Chessboard consider that every space on the board is at an intersection of two curved diagonal arcs of like-colored spaces. Each of these diagonal arcs extends from a space on the outer circle of spaces through successive circles into the center of the board, moving one space clockwise (or counterclockwise) for every successive circle transited. The arc continues through the center of the board and back out to the outer circle, always curving in the same direction.

The Bishop may move to any space on the two curved diagonal arcs that intersect on the space it occupies, as long as there are no pieces or void spaces between it and its destination.

The Bishop may capture an opposing piece if the opposing piece occupies a space that constitutes a legal destination within the Bishop's range of movement. To capture, the Bishop is placed in the destination space and the opposing piece occupying the space is removed from the board.

While the Bishop is permitted to pass through the center-circle, it may NOT move across void spaces. Also, the Bishop may not occupy the center-circle or void spaces.

A Bishop may not make a move or capture that places its own King in check.

See Figure 4 for an example of spaces to which a Bishop might move.

+ The Queen

The Queen may move or capture in the manner of the Rook or in the manner of the Bishop.

A Queen may not make a move that returns it to the space from which it started.

A Queen may not make a move or capture that places its own King in check.

See Figure 5 for an example of spaces to which a Queen might move.

+ The King

The King may move to any space adjacent to it on the file, rank, or curved diagonal that passes through the space it occupies.

Movements of the King that cross the center-circle can be easily determined if the player keeps in mind that spaces directly across the center-circle from one another are considered adjacent spaces that are in the same file.

When a King occupies a space adjacent to the center-circle, the spaces it can move to that are across the center-circle are the one directly opposite the space it occupies and the two spaces on either side of the opposite space.

The King may capture an opposing piece if the opposing piece occupies a space that constitutes a legal destination within the King's range of movement. To capture, the King is placed in the destination space and the opposing piece occupying the space is removed from the board.

While the King is permitted to pass through the center-circle, it may NOT move across void spaces. Also, the King may not occupy the center-circle or void spaces.

A King may not make a move or capture that places it in check.

See Figure 6 for an example of spaces to which a King might move.

+ The Knight

The spaces to which the Knight may move can be found by starting from the space that the Knight occupies, and proceeding two spaces along the rank which it occupies, and then proceeding from that space, one space along the file; or by proceeding from the space that the Knight occupies, two spaces along the file, and then proceeding from that space, one space along the rank. Unlike all other pieces, the Knight is not blocked in its movement by other pieces that occupy intervening spaces. In other words, it is the only piece that may jump over other pieces.

Movements of the Knight that cross the center-circle can be easily determined if the player keeps in mind that spaces directly across the center-circle from one another are considered adjacent spaces that are in the same file.

The Knight may capture an opposing piece if the opposing piece occupies a space that constitutes a legal destination within the Knight's range of movement. To capture, the Knight is placed in the destination space and the opposing piece occupying the space is removed from the board.

While the Knight is permitted to pass through the center-circle, it may NOT move across or jump over void spaces. Also, the Knight may not occupy the center-circle or void spaces.

A Knight may not make a move or capture that places its own King in check.

See Figure 7 for an example of spaces to which a Knight might move.

+ The Pawn

The Pawn always moves forward; never backward, sideways, or diagonally. ("Forward" is a relative term in Circular Chess. It is defined as "toward the center of the board" if the Pawn has not crossed the center and is defined as "away from the center of the board" if the Pawn has crossed the center. Due to the way a Pawn captures, "forward" is not necessarily the direction of the opponent's first rank.)

From its starting position, the pawn may move one or two spaces toward the center of the board, along the file that it occupies. From any space other than its starting position, it may move only one space forward along the file that it occupies.

A movement of a Pawn that crosses the center-circle can be easily determined if the player keeps in mind that spaces directly across the center-circle from one another are considered adjacent spaces that are in the same file.

See Figure 8 for an example of spaces to which a Pawn might move from its starting position. See Figure 9 for an example of the space to which a Pawn might move from a subsequent position.

The Pawn is the only piece that captures differently than the way it moves. Rather than capturing pieces that occupy spaces within its range of movement, a Pawn may capture any piece that occupies a space that is one space diagonally forward of the space the Pawn occupies. A Pawn captures pieces across the center-circle that occupy spaces to either side of the space exactly opposite the space the Pawn occupies.

See Figures 10 and 11 for illustrations of possible captures for a Pawn.

If a Pawn has passed over the center-circle and occupies a space on its opponent's fourth rank, it may capture an opposing Pawn "en passant." A Pawn may capture "en passant" only on the turn immediately following the movement of the Pawn to be captured. And the Pawn to be captured must have been moved from the space it occupied at the start of the game to a space adjacent to the capturing Pawn. To capture in this case, the capturing Pawn is placed on the space in the opponent's third rank that is between the space on which the captured Pawn began the game and the space to which it moved. The captured Pawn is removed from the board.

See Figure 12 for an illustration of an "en passant" capture where White's Pawn has crossed the center and Black's Pawn has moved two spaces from its starting position on the previous move. White may now capture Black's Pawn "en passant" by placing its own Pawn on the indicated space and removing Black's Pawn from the board. If White chooses not to capture Black's Pawn "en passant" on this move, it may not capture it "en passant" on subsequent moves.

While the Pawn is permitted to pass through the center-circle, it may not occupy the center-circle or void spaces.

A Pawn may not make a move or capture that places its own King in check.

+ Castling

Under certain conditions, the Rook and King may both be moved in the course of one turn. This repositioning of a Rook and King is called "Castling". Castling can be performed on either the King's side or the Queen's side.

The conditions under which a Rook and King may be Castled are as follows: If (I) neither the King nor the Rook has yet been moved, (ii) no piece is occupying a space on the arc of spaces between the King and Rook, (iii) no opposing piece is attacking a space on the arc of spaces between the King and Rook, and (iv) the King is not in check.

When Castling, the King is moved to a space on the first rank, two spaces away from the space it occupied. The Rook is then placed in the space on the opposite side of the King. The King always moves two spaces when Castling, while the Rook may move two or three spaces, depending on the side on which Castling is performed.

See Figure 13 for an illustration showing the final positions of a Rook and King after Castling. White has Castled on the King's side and Black has Castled on the Queen's side.

o Pawn Promotion

Just as in traditional Chess, when a Pawn reaches its opponent's first rank, it may be promoted. When promoting a Pawn, the Pawn is immediately removed from the board and is replaced with a piece of the player's choice having higher value. This is done before the opponent's next turn.

In Circular Chess it is also possible for a Pawn to reach its OWN first rank. Depending on its starting position and the number and direction of captures it makes during the course of a game, it may end up moving "forward" toward its own side of the board. In this case, when a Pawn reaches its own side's first rank, the Pawn may also be promoted.

o Check

A player's King is in "check" when the player's opponent can capture the King on the opponent's next move. When a player concludes a move such that the opposing King is in "check", that player must announce this by saying, "Check." A player may not conclude a move that leaves that player's own King in "check."

o Checkmate

A player's King is "checkmated" when the player's King is in check, and the player cannot conclude a move such that the King is not in "check."

o Winning Games

A player wins the game when the player's opponent's King is "checkmated", or when the player's opponent resigns the game.

o Drawing Games

When a player is not in "check", but has no legal move, the game is "stalemated", and the game ends in a draw.

If neither player has more material than a King and a Bishop or a King and a Knight, there is insufficient material for either player to achieve mate. The game ends in a draw.

If fifty consecutive moves have been made by each player without a piece being captured or any Pawns being moved, then the player who is to move may declare a draw.

If the same arrangement of pieces appears on the board three times, with the same player to move each time, then the player who's turn it is to move may declare a draw. If a player is in a position to produce, in one move, the same arrangement of pieces that occurred twice before, with the opponent to move each time, that player may declare a draw.

"The same arrangement of pieces" is to be understood as when pieces of the same kind and color occupy the same spaces.