Chess960

Chess with the back rank shuffled. Every game starts from one of 960 starting positions, so memorized openings don’t help: you play from the first move. It’s also known as Fischer Random Chess, after Bobby Fischer, who proposed it in 1996.

Everything is ordinary chess except the starting position and how castling looks. If you know chess, you know Chess960.

The starting position

The pawns stand where they always do. Behind them, White’s pieces are shuffled, with two rules:

• the bishops stand on squares of opposite colors;
• the king stands somewhere between the two rooks.

Black’s pieces mirror White’s, file by file. One of those 960 positions is the standard chess setup.

With a random start, only the pawns stand on the board while the match waits for its players, so nobody sees the position before the game begins; the pieces are set up the moment the match starts. A position chosen in the match settings (below) is on the board from the start, so everyone who joins sees it too. The position’s number shows under the board for the whole match (and in the move list’s first line, Match started), so you can play it again: pick Choose in the match settings and enter that number.

How to play

Click one of your pieces to select it — the squares it can legally move to are highlighted. Click a highlighted square to make the move. White moves first, and players alternate turns.

Castling

Castling works as in chess: the king ends on the g-file with the rook next to it on the f-file when castling toward the h-side, or on the c-file with the rook on the d-file toward the a-side. Only the starting squares differ, so the king may move several squares, one, or not at all — and so may the rook.

To castle, click your king, then the rook you’re castling with — or, as in chess, the square the king lands on (g1 or c1). Both are highlighted when castling is allowed. When the king could also just step onto that square, clicking it makes that ordinary move; click the rook to castle instead. You may castle only if neither piece has moved yet, every square both of them cross or land on is empty (apart from the two of them), and the king isn’t in check, doesn’t pass through an attacked square and doesn’t land on one.

The rest of the rules

Standard chess movement:

• Pawn — moves forward one square (or two from its starting rank), captures one square diagonally.
• Knight — moves in an “L”: two squares one way and one square perpendicular. Jumps over pieces.
• Bishop — any distance diagonally.
• Rook — any distance horizontally or vertically.
• Queen — any distance in any straight line (rook + bishop).
• King — one square in any direction.

And:

• En passant — when a pawn advances two squares and lands beside one of your pawns, your pawn may capture it as if it had moved only one — on the very next move only.
• Promotion — a pawn reaching the far rank becomes a queen, rook, bishop or knight: pick one from the choice that appears.

You may not make a move that leaves your own king in check. The game ends in:

• Checkmate — the king is in check and has no legal escape. The attacker wins.
• Stalemate — the player to move has no legal move but is not in check. Drawn.
• Insufficient material — checkmate has become impossible for both sides, no matter how anyone plays. Drawn.
• Threefold repetition — the same position appears for the third time. Drawn.
• 50-move rule — fifty moves by each player without a capture or a pawn move. Drawn.

Match settings

• Starting position — Random (the usual way to play), or Choose and enter a position number from 0 to 959 to play a particular position again. 518 is the standard chess setup. A chosen position is never a secret: the match’s settings and its board show it to everyone before they join.
• Repetition and 50-move draws — Automatic (the default) ends the game in a draw as soon as either happens. By claim (FIDE) only lets the player to move claim a draw, with the Claim draw button; if nobody claims, play goes on until the position appears a fifth time or 75 moves by each player pass without a capture or a pawn move.

Credits

A variant of this platform’s Chess. The piece sets are public domain (CC0): rhosgfx by RhosGFX (from lichess), and silhouette from Openclipart.