Chess960 vs Computer

How to play Chess960 (Fischer Random chess)

Chess960 — also called Fischer Random chess — is ordinary chess with one dramatic twist: the pieces on each player’s back rank are shuffled before the game begins. World Champion Bobby Fischer introduced the variant in 1996 because top-level chess had become, in his view, a contest of memorised opening theory: grandmasters were reciting twenty prepared moves before the real thinking started. By randomising the starting position, every game begins as unexplored territory, and both players must rely on understanding, calculation and creativity from move one. There are exactly 960 legal starting arrangements, which gives the game its name. Everything else — how the pieces move, check, checkmate, en passant, promotion — is standard chess, with one carefully redesigned rule: castling. Play a friend on one screen, or take on the computer at three difficulty levels and earn ranking points.

The goal

Exactly as in classical chess: checkmate the enemy king — attack it so that it cannot escape, be shielded, or have the attacker captured. White always moves first. If the player to move has no legal move but is not in check, the game is a stalemate and ends in a draw.

The starting position

The pawns stand on their usual second rank, just like normal chess. The eight back-rank pieces (two rooks, two knights, two bishops, queen and king) are arranged randomly, subject to two constraints that keep the game sound: the two bishops must start on opposite-coloured squares (one light, one dark), and the king must start somewhere between the two rooks — so that castling to either side remains possible. Black’s pieces always mirror White’s, square for square. Counting every arrangement that satisfies those rules gives exactly 960 distinct positions, and the traditional chess setup is one of them.

The numbering scheme (position #0–959)

Each of the 960 positions has a standard number, computed the same way everywhere (the Scharnagl scheme): the number is repeatedly divided to place first the light-squared bishop (among files b, d, f, h), then the dark-squared bishop (among a, c, e, g), then the queen on one of the six remaining files, then the pair of knights on two of the five files still free; the last three empty files receive a rook, the king and the other rook, in that order — which automatically puts the king between the rooks. Under this scheme, position #518 is exactly the classical chess array (RNBQKBNR). In this app you get a daily position — the same number for every player on the same UTC day — shown as “Position #N” above the board, and the New Position button deals a fresh random one whenever you like. Note the number if you want to replay or share a setup.

Castling in Chess960 — read this carefully

Castling is the one rule that changes, because the king and rooks can start almost anywhere. The key idea is simple: no matter where the king and rook begin, they always FINISH on the squares they would occupy after castling in normal chess. Castling with the h-side rook (“kingside”) puts the king on g1 and that rook on f1; castling with the a-side rook (“queenside”) puts the king on c1 and that rook on d1 (g8/f8 and c8/d8 for Black). Depending on the starting position, the king or the rook may travel a long way, one square, or not move at all. The conditions mirror classical chess:

• Both pieces must be untouched: neither the king nor the chosen rook may have moved earlier in the game. Moving a rook forfeits castling with that rook only; moving the king forfeits castling on both sides — even if the piece later returns to its starting square.
• All squares between the king’s start and its destination, and between the rook’s start and its destination, must be empty — except that the king and the castling rook themselves do not block each other (they may stand on, or pass through, each other’s squares).
• The king may not castle out of, through, or into check: its starting square, every square it crosses, and its destination square must not be attacked by any enemy piece. The rook’s path, as in normal chess, is allowed to pass through attacked squares.
• Special cases are perfectly legal and common: if the king already stands on its destination (for example on the c-file castling queenside), only the rook moves; if the rook already stands on its destination, only the king moves. Castling can even be available on move one in some positions.
• How to castle in this app: tap your king, then tap the rook you want to castle with (a ring appears on it). “King takes own rook” is the standard, unambiguous way to enter a Chess960 castle, since the king’s destination square can clash with its ordinary moves.

Everything else is normal chess

• Pieces move, capture, check and checkmate exactly as in classical chess. Pins, forks, discovered attacks — all the familiar tactics apply from the very first move.
• Pawns start on their usual rank, so the two-square first step and the en passant capture work exactly as in normal chess.
• A pawn reaching the last rank promotes; in this app it is automatically promoted to a queen, by far the most common choice.

Winning, drawing and undo

Checkmate ends the game immediately — the status banner names the winner. If the side to move has no legal move but is not in check, the game is drawn by stalemate. In the two-player game, the Undo button takes back the last move (use it as many times as you like), New Game restarts the same numbered position, and New Position deals a different random setup.

Playing the computer (ranked)

In “Chess960 vs Computer” you pick the starting position (keep the daily one or re-roll), your colour and one of three levels. Easy blunders on purpose so newcomers can win; Normal looks ahead and punishes mistakes; Expert searches deepest and rarely misses a tactic. The computer thinks entirely on your device, so it works offline. Beat it to earn ranking points — Easy +10, Normal +30, Expert +100 — and sign in to put your best result on the leaderboard.

Strategy tips

• Spend your first moments just reading the position: which diagonals will your bishops open onto, which pawns are undefended, where will your king be safest? In Chess960 the “opening” is decided by observation, not memory.
• Watch for immediate tactics. In many positions a bishop or queen in the corner aims at an unprotected enemy pawn from the very start — games can be decided by move three if a player develops on autopilot.
• Castle early. Because the king can start on an awkward central file, tucking it away on the g- or c-file is often even more urgent than in classical chess — and remember that one king move throws the right away.
• Classical principles still apply: fight for the centre, develop knights and bishops before the queen, do not move the same piece twice without reason, and connect your rooks once the king is castled.

Frequently asked questions