Draughts

Draughts, also known as checkers, is a group of board games which involve the "jumping" of enemy pieces. The name "draughts" is preferred by English players and others in the United Kingdom and its former colonies and territories. The exceptions to this are the United States, Canada and Australia, where the name "checkers" is preferred. This article treats both names as synonyms, though the longstanding name "draughts" is used except in specific references to the game in these countries, where "checkers" is used.

History
Early evidence has been found of a similar game played in ancient Egypt, and mentions of the game had been made by Plato and Homer in the first few centuries BC. Egyptian origins can be traced as far back as 1600 BC.

Ancient games
A similar game has been played for thousands of years. A board resembling a draughts board was found in Ur dating from 3000 BC. In the British Museum are specimens of ancient Egyptian checkerboards, found with their pieces in burial chambers, and the game was played by Queen Hatasu. Plato mentioned a game, πεττεια or petteia, as being of Egyptian origin, and Homer also mentions it. The method of capture was placing two pieces either side of the opponent's piece. It was said to have been played during the Trojan War. The Romans played a derivation of petteia called latrunculi, or the game of the Little Soldiers.



Alquerque
An Arabic game called Quirkat or al-qirq, with similar play to modern draughts, was played on a 5×5 board. It is mentioned in the 10th century work Kitab al-Aghani. Al qirq was also the name for the game that is now called Nine Men's Morris. Al qirq was brought to Spain by the Moors, where it became known as Alquerque, the Spanish derivation of the Arabic name. The rules are given in the 13th century book Libro de los juegos. In about 1100, probably in the south of France, the game of Alquerque was adapted using backgammon pieces on a chessboard.

Evolution
The game pieces of draughts in 1100 AD were called "ferses", the name that was given to chess queens in this time period, and the draught ferses moved in the same way as the queen did in chess. Note however that at this time the queen was able to move only one square per turn. The one new move this game introduced was the ability to jump over an opponent's pieces and take them. At this time the game was known as "Fierges".

In Philip Mouskat's "Chronique" (1243) is a reference to the use of "Kings", suggesting that the ability to promote a piece existed at this time.

When in Chess "ferses" were renamed to "Dame", the same occurred in Draughts, and the game's name also changed to "Dames". While it is thought that the original Fierges had a compulsory capture rule, there is no evidence that this rule existed in Dames. This rule was however reintroduced in France in 1535. Modern play includes this rule.

The name "Checkers" originated with European settlers in the United States. The version of checkers most often played in the United States is identical to the English variant of draughts, though there are some regional variants of checkers, such as pool.

In the 18th century an anonymous Pole invented the variant of draughts that is played on a 10x10 board with 2x20 pieces. This variant was called Polish draughts and was later called international draughts.

General rules
Draughts is played by two people, on opposite sides of a playing board, alternating moves. One player has dark pieces, and the other has light pieces. Pieces move diagonally and pieces of the opponent are captured by jumping over them.

The English variant
The English variant is played on an 8x8 board with 2x12 pieces that can only move and capture forward. This is the same variant as American checkers.

Rules
The rules of this variant of draughts are:
 * Board The draughts board is an 8 by 8 grid, with alternating dark and light squares (forming a "checkered" pattern, from which the game gets its North American name). The playable surface consists of the 32 dark squares only. A consequence of this is that, from each player's perspective, the left and right corners encourage different strategies.
 * Pieces The pieces are usually made of wood and are flat and cylindrical. They are invariably split into one darker and one lighter color. Traditionally, these colors are Red and White. There are two kinds of pieces: normal and "king". King pieces are differentiated as consisting of two normal pieces of the same color, stacked one on top of the other. U.S. checkers sets typically consist of red and black plastic pieces with ridges or scallops on the perimeter to aid stacking. The board is red and black, with play on the black squares only. On these sets, black plays first. Often, the checkers board is also equipped with a backgammon board on the reverse, with 15 of each color piece supplied for playing that game.
 * Starting Position: Each player starts with 12 pieces on the three rows closest to their own side, as shown in the diagram. The row closest to each player is called "King Row". The Red side moves first.
 * How to Move: There are two ways to move a piece: simply sliding a piece forward to an adjacent and unoccupied dark square, or "jumping" a piece of the opposing player. It is possible for a piece to be "jumped" if on one side there is an opposing piece and the opposite side is vacant. In this case, one piece would "jump over" the other into the vacant square on the opposite side. A piece that is jumped is captured and removed from the board. Multiple-jump moves are possible if when the jumping piece lands there is another opposing piece with a vacant square on the opposite side. Jumping is mandatory and cannot be passed up to make a non-jumping move, nor can fewer than the maximum jumps possible be taken in a multiple-jump move. If it is possible to make two jump moves, the player is free to choose which to make regardless of whether one is a multiple-jump move.
 * Kings: If a player's piece moves into the King Row on the opposing player's side of the board, that piece is said to be "kinged" and gains the ability to move in both forward and backward directions. If player's piece jumps into King Row, it cannot jump out (as in a multiple-jump move) until that move has ended and the piece has been kinged.
 * How the Game Ends: A player wins by capturing all of the opposing player's pieces, or by leaving the opposing player with no legal moves.

In tournament draughts, a variation called three-move restriction is preferred. The first three moves are drawn at random from a set of accepted openings. Two games are played with the chosen opening, each player having a turn at either side. This tends to reduce the number of draws and can make for more exciting matches. Three-move restriction has been played in the United States championship since 1934. A two-move restriction was used from 1900 until 1934 in the United States and in the British Isles until the 1950s. Before 1900, championships were played without restriction: this style is called go-as-you-please.

One rule of long standing that has fallen out of favor, though still used in some homes, is the huffing rule. In this variation, jumping is not mandatory, but a piece that could have jumped, but failed to do so, may be taken (huffed) by the opposing player at the beginning of his or her next turn, much as the en passant pawn capture in chess. After huffing the offending piece, the opponent then takes his or her turn as normal. Huffing has been abolished by the American Checker Federation.

Two common misinterpretations of the rules are,
 * that the game ends in a draw when a player has no legal move but still pieces remaining (true in Chess but not in checkers)
 * that capturing with a king precedes capturing with a regular piece

Computer players
The first computer draughts programme was written by C. S. Strachey M.A. National Research Development Corporation, London, England, in the early 1950s. See—Proceedings of the Association for Computing Machinery Meeting, Toronto, 1952. The second computer player of checkers was written in 1956 by Arthur Samuel, a researcher from IBM. Other than it being one of the most complicated game playing programs written at the time, it is also well known for being one of the first adaptive programs. It learned by playing games against modified versions of itself, with the victorious versions surviving. Samuel's program was far from mastering the game, although one win against a blind checkers master gave the general public the impression that it was very good. Samuel didn't mention his opponent was blind!

In the 1990s, the strongest program was Chinook written by a team led by Jonathan Schaeffer. Marion Tinsley, world champion from 1955-1962 and 1975-1991, won a match against the machine in 1992. In 1994, he had to resign in the middle of an even match because of health reasons; he died shortly thereafter. Chinook defended its man-machine title against Don Lafferty, and won the US national tournament in 1996 with a big margin. Chinook was retired after that tournament. The man-machine title was never contested again.

The best PC programs of today are stronger than the best humans, and also stronger than Chinook was at the time when it won the man-machine title. In addition, today's PCs are much faster than Chinook's hardware.

Computational complexity
It was generally expected that draughts will not be solved by 2010. However, this prediction, wherever it came from, did not hold, as draughts was, in fact, solved sometime during 2006-2007. 

The number of legal positions in draughts is estimated to be 1018, and it has a game-tree complexity of approximately 1031.

When draughts is generalized so that it can be played on an n-by-n board, the problem of determining if the first player has a win in a given position is EXPTIME-complete.

Recently it was announced by the Chinook team that the tournament opening the White Doctor (10-14 22-18 12-16) had been proved to be a draw.

Famous checkers players

 * Walter Hellman
 * Asa Long
 * Marion Tinsley

Other variants
Here are some important terms to know: Below is a list of the most popular variants of draughts. The rules of these variants are exactly the same as they are mentioned below.
 * Flying kings - kings that can move as far as they want in diagonals like a bishop in chess. However, flying kings cannot capture like a Bishop.
 * Crownhead or Kings Row - the farthest row forward where men become kings when they touched this row.
 * International draughts - The board size is 10x10 with 20 pieces on each side and has flying kings. White pieces moves first. If there are many sequences to capture, you have to capture the sequence that has the most pieces. If a man touches the kings row from a jump and it can continue to jump backwards, it has to jump backwards, but it is not kinged. It is mainly played in the Netherlands, France, some eastern European countries, some parts of Africa, some parts of the former USSR, and other European countries. This is the most popular variant of draughts.
 * Brazilian checkers - Exactly the same rules as international draughts, but it's played on a 8x8 board. It is mainly played in Brazil.
 * Canadian checkers - Exactly the same rules as international draughts, but it's played on a 12x12 board with 30 pieces on each side. It is mainly played in Canada.
 * Pool checkers - Exactly the same rules as Brazilian checkers but does not have the "capture the sequence that has the most pieces" rule. There is another different rule between brazilian checkers in which black moves first, instead of white. It is mainly played in the South-Eastern states in the United States.
 * Spanish checkers - Also called Spanish pool checkers. Men cannot jump backwards. Exactly the same rules as Brazilian checkers, but if there are many sequences to capture, you have to capture the sequence that has the most pieces. If there are still more sequences, you have to capture the sequence that has the most kings. The board is mirrored (the left side is fliped to the right side and vice versa). It is mainly played in some parts in South America and some Northern African countries.
 * Russian checkers - Also called shashki checkers or Russian shashki checkers. Exactly the same rules as brazilian checkers, but if a man touches the kings row from a jump and it can continue to jump backwards, it has to jump backwards as kings, not men. It is mainly played in some parts in Russia, some parts of the former USSR, and Israel.
 * Italian checkers - Men cannot jump kings and men cannot jump backwards. If there are many sequences to capture, you have to capture the sequence that has the most pieces. If there are still more sequences, you have to capture with a king instead of a man. If there are still more sequences, you have to capture the sequence that has the most kings. If there are still more sequences, you have to capture the sequence that has a king first. The board is mirrored (the left side is fliped to the right side and vice versa). It is mainly played in Italy, and some Northern African countries.
 * Suicide checkers - Also called anti-checkers, giveaway checkers or losing draughts. You have to give away all of your pieces or block all of your pieces to win i.e. stop yourself from having a legal move.
 * Russian poddavki checkers - Suicide version of Russian checkers.
 * In Turkish draughts pieces move straight forwards or sideways, kings moving like a rook in chess, so that both red and black squares are used. Each player starts with 16 pieces in the first two rows. It is played in the same locations as Russian checkers.

Halma and Chinese checkers
Halma is a game in which pieces can move in any direction and jump over any other piece, friend or enemy. Pieces are not captured. Each player starts with 19 (2-player) or 13 (4-player) pieces all in one corner and tries to move them all into the opposite corner. Halma is actually a very different game than checkers.

Chinese checkers is based on Halma, but uses a star-shaped board divided into triangles. Contrary to its name, this game is not of Chinese origin, nor is it based on checkers.