Four-player chess for themselves. As with regular chess, four-player chess begins with fortifications and the of pieces, but opportunities for capturing pieces (and gaining points) come about at large as each of the three opponents likewise do attacks and make threats of capture. Therefore picking friends and enemies has a political quality; ultimately the impromptu teammates will have to combat each other as only one can win. The Cox-Forbes theory of the origin of chess, though debunked, asserts that a four-player version was the earliest form of the game. A description of a four-player chess game is found in an Indian text
Chess and is provably less than 10, with a game-tree complexity of approximately 10. The game-tree complexity of chess was first calculated by Claude Shannon as 10, a number known as the Shannon number. Typically an average position has thirty to forty possible moves, but there may be as few as zero (in the case of checkmate or stalemate) or (in a constructed position) as many as 218. Chess has inspired many combinatorial puzzles, such as the knight's tour and the eight queens puzzle. The idea of creating a chess-playing machine dates to the 18th century; around 1769, the chess-playing automaton