How to play chess: rules, clocks and rating
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Chess is played by two players on a board of 64 squares. The aim is to attack your opponent's king so that it cannot escape: checkmate. This guide covers the rules, time controls and ratings of chess on Boombala.
How the pieces move
| Piece | Move |
|---|---|
| King | One square in any direction. |
| Queen | Any number of squares along a rank, file or diagonal. |
| Rook | Any number of squares along a rank or file. |
| Bishop | Any number of squares along a diagonal. |
| Knight | An "L": two squares straight, one to the side. The only piece that jumps over others. |
| Pawn | One square forward (two on its first move); captures one square diagonally forward. |
Special moves
- Castling: if the king and a rook have not moved, the squares between them are empty and the king is not in check, the king moves two squares toward the rook and the rook jumps to its other side. The king may not pass through an attacked square.
- En passant: when a pawn advances two squares and lands beside an enemy pawn, that pawn may capture it on the very next move as if it had moved one square.
- Promotion: a pawn reaching the last rank becomes a queen, rook, bishop or knight.
How a game ends
- Checkmate: a player whose king is attacked and has no move to save it loses.
- Resignation: a player resigns. Leaving the table mid-game counts as resigning.
- Time: running out of time loses, unless the opponent lacks the material to ever checkmate: then it is a draw.
- Abandoning: if your opponent makes no move for a minute (20 seconds if they left the table), you are asked whether you want to wait. If you do not, you win.
- Draws: stalemate (no legal move but not in check), agreement, fifty moves without a capture or pawn move, the same position three times, and insufficient material (such as king and bishop against king).
Time controls
Written like "5 + 0": the first number is each player's minutes, the second the seconds added after every move. Each player's first move is free. Pairing offers 1+0, 3+2, 5+0, 10+0 and 15+10; at your own table you can also play without clocks.
Elo rating
Rated games use FIDE's Elo system. Everyone starts at 1500. After a game your rating changes by K × (result − expected result), where a win is 1, a draw 0.5 and a loss 0. The expected result comes from the rating difference (counted as at most 400). K is 40 for your first 30 games, then 20, and 10 once you have reached 2400.
Example
Ayşe, rated 1500, beats Can, rated 1700. Her expected result is about 0.24. With K = 20 she gains 20 × (1 − 0.24) ≈ +15 and Can loses 15. Pairing looks for someone close to your rating, and the accepted gap widens by 50 points every 10 seconds you wait.
Games against the computer (Stockfish) never change your rating, so feel free to try out openings.