Chess
The whole game, including the parts people forget: castling through check, en passant, and the five different ways a game can end level.
How the pieces move
- The king moves one square in any direction. It may never move onto a square that is attacked.
- The queen moves any distance in a straight line: along a rank, along a file, or on a diagonal.
- A rook moves any distance along a rank or a file.
- A bishop moves any distance diagonally, and therefore stays on its starting colour all game.
- A knight moves in an L: two squares along one line and one square across. It is the only piece that jumps over others.
- A pawn moves one square straight forward, or two squares from its starting position, and captures one square diagonally forward. It can never move backwards.
The special moves
- Castling moves the king two squares towards a rook and the rook to the square the king passed over.
- Castling is only legal if neither that king nor that rook has moved, the squares between them are empty, and the king does not start, cross or finish on an attacked square.
- En passant: a pawn that advances two squares and lands beside an enemy pawn may be captured by it as if it had moved only one square. This is only available on the very next move.
- A pawn reaching the far rank must be promoted, to a queen, rook, bishop or knight of its own colour. Almost always a queen.
Check and checkmate
- A king under attack is in check. You must answer it immediately: move the king, capture the attacker, or block the line.
- You may never make a move that leaves your own king in check.
- Checkmate is a king in check with no legal move that ends the check. That wins the game at once.
The five ways a game is drawn
- Stalemate: the player to move has no legal move but is not in check.
- Threefold repetition: the same position occurs three times.
- The fifty-move rule: fifty moves by each player with no capture and no pawn move.
- Insufficient material: neither side has enough pieces left to deliver checkmate.
- Agreement: one player offers a draw and the other accepts.
How a game ends
- Checkmate wins immediately.
- Any of the five draws above ends the game level, and the first four are detected automatically without either player having to claim them.
- A resignation ends the game and the other player wins.
- A missed move deadline is a loss, exactly like resigning.
The server validates every move, so an illegal move is not possible here and neither is missing that you are in check. Stalemate, repetition, the fifty-move rule and insufficient material are all detected automatically and end the game as a draw without anybody having to claim them.
Chess terms
- Check
- Your king is attacked and you must deal with it this move.
- Checkmate
- Your king is attacked and nothing can be done about it. The game is over.
- Stalemate
- You have no legal move but you are not in check. A draw, not a loss.
- En passant
- Capturing a pawn that has just used its two-square move, as though it had moved only one.
- Castling
- The one move that shifts two pieces: the king two squares towards a rook, and the rook past it.
- Promotion
- A pawn reaching the last rank becomes another piece, almost always a queen.