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Overview:
The chess game featured on the site can be played against your opponent in real-time or gradually over the course of several days. Each player is rated according the official Elo chess rating system, with new players starting with an initial 1000 points.
Getting Started:
To start a game, either join an open table or create a new one. As the creator of a new table, you can choose your color and the maximum turn time limit. The maximum turn time limit can be set to any value between 24 and 120 hours. If a player takes longer than that period of time to take his turn, he automatically loses the game.
To move a piece, simply click and drag the piece you want to move to its new location. The game will prevent you from making an illegal move, such as a move that would leave your king your check.
Ending the Game:
The game ends in a win if one player places his opponent in checkmate, if a player resigns, or if a player exceeds his turn time limit. The game can end in a draw if a stalemate is reached or due to the 50 move rule. A stalemate occurs if a player has no legal moves to make but his king is not presently in check. The 50 move rule dictates that a draw occurs if no pawns have been moved and no captures made for 50 consecutive moves. The game will display a warning when there are 10 moves remaining before a draw can be reached in that manner.
Rating System:
At the conclusion of each game, the players' chess ratings are updated based on the outcome if the game did not end in a draw. The change in a player's rating is based on the difference between his score and his opponent's. First, the probability of the weaker player winning is calculated using this equation:
Probability = 1 / (1 + (10 ** (Difference in Ratings / 400)))
If the higher rated player wins, the probability is reversed: Probability = 1 - Probability.
A constant (K) is then determined based on how many games the player has played and his current score:
K = 30 for new players
K = 20 after 10 games have been played
K = 15 for players rated higher than 2000.
The winner's score increases by: K * (1 - Probability)
The loser's score decreases by: K * Probability
Browser Compatibility:
The game should be cross-browser compatible, but there is one known issue with IE 6. Due to bugs in the way IE 6 handles PNG images, it is unable to properly redraw the image of a pawn if it is promoted to a queen. This should be fixed in IE 7, although we haven't tested it. A current version of Mozilla or Firefox is recommended.
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