A Game Courier Preset for Chess66

This preset enforces the rules and displays legal moves.

Chess66

Rules enforced. Legal moves displayed.

Welcome to Game Courier, where you can play Chess66 and many other Chess variants through online correspondence.

Rules of Chess66

Chess66 is an adaptation of Chess to a board with a different geometry. Where no difference from Chess is noted, it follows the rules of Chess.

1. Its board has two extra spaces that each overlap with a neighboring space and push the rank it is on over by half a space. A4 overlaps with a4, pushing the 4th rank half a space right. H5 overlaps with h5, pushing the 5th rank half a space left.
2. Because its ranks and files no longer line up neatly on a Cartesian grid, movement is based only on geometrical relations and not on the coordinate system.
3. Lateral movement is allowed through the sides of spaces, and lateral movement in the same direction goes through the opposites sides of spaces. Because of this, vertical movement may sometimes shift the file named by the coordinate system.
4. Diagonal movement is allowed through the corners of spaces that do not share any sides, and diagonal movement in the same direction goes through the corners at opposite ends of spaces.

A Switch is a pair of overlapping spaces that come together at one end and branch off at the other. In doing so, they allow some new movement options:

1. At its narrow end, each space in a Switch shares the same side with an adjacent space. This allows a Rook or Queen to move through the narrow end to one of two different files. In this way, a Rook or Queen can checkmate a King without assistance from another piece.
2. From the broad end, a Rook or Queen can move through the Switch to the same file, providing a new way for double attacks to work.
3. Also at the narrow end, each space in a Switch shares a corner with another adjacent space that neither one shares any sides with. Through this corner, diagonal movement is able to change color. So, a Bishop that moves to A4 or to H5 may move away on a subsequent turn on a different color. This allows Bishops to switch color, giving a Bishop the power to reach every space on the board.

Although the two spaces in a Switch overlap, they count as separate spaces.

1. A piece moving to a Switch must move to one space or the other. For example, a Pawn on a2 can make a double move to either A4 or a4.
2. While some paths can lead to either Switch, others lead to only one space or the other in a Switch. For example, a Bishop on e8 can go to A4 or h5, and a Bishop on d1 can go to a4 or H5.
3. The movement options available to a piece on a Switch depend upon which space of the Switch it is on. For example, a Pawn on A4 can proceed only to a5, and a Pawn on a5 can proceed only to b5. Also, a Bishop on A4 can move away on either light or dark spaces, but one on a4 can move away only on light spaces.

Because the two spaces in a Switch overlap, they are treated as the same space in some respects:

1. The two spaces in a Switch cannot be occupied simultaenously.
2. It is illegal to pass through a space in a Switch if the other space is occupied.
3. A piece may move to a space in a Switch only if both spaces in it are empty or one is occupied by an enemy piece. If a piece moves to the empty space in a Switch, and the other space is occupied by an enemy piece, that piece is considered captured.
4. It is not legal to move from one space in a Switch to the other. Instead, A4 is treated as though it were horizontally adjacent to b4, and H5 is treated as though it were horizontally adjacent to g5. This affects the movement options for Rooks, Queens, Kings, and Knights

The King leaps one space in any lateral or diagonal direction. It may castle with a Rook on its first move so long as it is not in check, there is nothing in between it and the Rook, it doesn't pass through check while castling, and the Rook hasn't moved. In castling, it moves two spaces toward the Rook, and the Rook moves to the space the King passed over.

The Queen may move as a Rook or a Bishop.

The Rook may move any number of spaces in any lateral direction until it reaches an occupied space or Switch.

The Knight can leap directly to any space that could be reached in two one-space moves except for those reachable by a Rook or Bishop. Since it's a one-space move from A4 to b4 or from H5 to g5, a Knight on A4 or H5 can leap further away than a Knight can normally leap.

A Bishop may move any number of spaces in any diagonal direction until it reaches an occupied space or Switch.

The Pawn may move one space straight forward without capturing, or it may move one space diagonally forward to capture. On its first move, it may move two spaces forward without capturing so long as it isn't blocked. If this move takes it over a space an enemy Pawn could have captured it on, that Pawn may immediately capture it by en passant, moving to the space it passed over. On reaching the last rank, it must promote to another piece. This may be any piece except a King or another Pawn.

How to Move Pieces

Full Algebraic Notation

Algebraic notation identifies each space by a coordinate that begins with its file label and ends with its rank label. On the Chess board, files go up and down from one player to the other, and ranks go from left to right. In most games, files are represented by letters, and ranks are represented by numbers, but there is no fixed rule requiring this for all games, and some games, such as Shogi, reverse this convention. If you look at the diagram, you will usually see the file labels going from left to right and the file labels going up and down. And if you hover your mouse over a space, you will normally see the name of the coordinate appear in a tooltip.

It is not uncommon to see algebraic notation being used for Chess, but it is often in an abbreviated format that requires you to know both the rules of the game and the current position to know exactly which piece moves where. For example, the notation "Ne6" indicates that a Knight is moving to e6, but it doesn't indicate which Knight, and it doesn't specify where the Knight is coming from. To figure this out, you need to know how a Knight moves and which Knight on the board can make a legal move to e6.

Although rules may be programmed for individual games, Game Courier itself does not know the rules of any game, and it is unable to parse abbreviated algebraic notation. Therefore, it relies on full algebraic notation, which completely specifies the move without requiring any knowledge of the game's rules or the current position. The most usual type of full algebraic notation indicates the piece that is moving by its label, the space it is moving from, and the space it moving to. In Chess, a typical first move might be written as "P e2-e4". When you hover your mouse over a piece, you will normally see the piece label followed by the coordinate for the space, and when you hover it over an empty space, you will normally see the coordinate label. Including the piece label in your notation allows Game Courier to check that the piece you're moving is the right one, and it makes game notation easier to follow, but it is not mandatory.

You may promote a piece by including a promotion move after your regular move. A promotion move has a piece go directly to a coordinate. Here is an example: "p e7-e8; q-e8".

You may remove a piece from a space by adding an @ to the space or by omitting the destination coordinate. For example, both "@-e4" and "e4-" would remove the piece on "e4". This is useful for en passant when you are playing a game that does not handle this automatically. For example, "P d5-e6; e5-" removes the Pawn on e5 after a Pawn moves from d5 to e6.

You will not need to remove spaces for most games, but if you should need to, you can do this by omitting the first coordinate in a move. For example, "-e4" would remove e4 from the board. To add or return a space to the board, you may add an @ or any other piece to it.

Available Pieces

Pieces are represented by labels, usually using uppercase letters for White and lowercase letter for Black. When you enter a move or specify the starting position for a game, you should remember that piece labels are case-sensitive. Many piece sets are available for use with Game Courier, and this table shows you which pieces belong to the piece set you are currently using.

The inclusion of a piece does not indicate that it is used in the game you are playing. But if your game uses pieces not included here, you should choose a different piece set.

Credits

This preset uses the test settings file for Chess66, which was made by Fergus Duniho.

Game Courier was created, programmed and written by Fergus Duniho.

Game Courier, Copyright © Fergus Duniho, 2001-2017