Chess Ideas

Chess is a two-player strategy board game played on a chessboard, a checkered gameboard with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide in homes, parks, clubs, online, by correspondence, and in tournaments. In recent years, chess has become part of some school curricula.
Each player begins the game with 16 pieces: one king, one queen, two rooks, two knights, two bishops, and eight pawns. Each of the six piece types moves differently. The objective is to 'checkmate' the opponent's king by placing it under an inescapable threat of capture. To this end, a player's pieces are used to attack and capture the opponent's pieces, while supporting their own. In addition to checkmate, the game can be won by voluntary resignation by the opponent, which typically occurs when too much material is lost, or if checkmate appears unavoidable. A game may also result in a draw in several ways, where neither player wins. The course of the game is divided into three phases: opening, middlegame, and endgame.
The first official World Chess Champion, Wilhelm Steinitz, claimed his title in 1886; the current World Champion is the Norwegian Magnus Carlsen. In addition to the World Championship, there are the Women's World Championship, the Junior World Championship, the World Senior Championship, the Correspondence Chess World Championship, the World Computer Chess Championship, and Blitz and Rapid World Championships. The Chess Olympiad is a popular competition among teams from different nations. Online chess has opened amateur and professional competition to a wide and varied group of players. Chess is a recognized sport of the International Olympic Committee and international chess competition is sanctioned by the World Chess Federation (FIDE), which adopted the now-standard Staunton chess set in 1924 for use in all official games. There are also many chess variants, with different rules, different pieces, and different boards.
Since the second half of the 20th century, computers have been programmed to play chess with increasing success, to the point where the strongest home computers play chess at a higher level than the best human players. In the past two decades computer analysis has contributed significantly to chess theory, particularly in the endgame. The computer Deep Blue was the first machine to overcome a reigning World Chess Champion in a match when it defeated Garry Kasparov in 1997.

Rules

The official rules of chess are maintained by the World Chess Federation. Along with information on official chess tournaments, the rules are described in the FIDE Handbook, Laws of Chess section.^[1]

Setup

Chess is played on a square board of eight rows (called ranks and denoted with numbers 1 to 8) and eight columns (called files and denoted with letters a to h) of squares. The colors of the 64 squares alternate and are referred to as "light" and "dark" squares. The chessboard is placed with a light square at the right-hand end of the rank nearest to each player, and the pieces are set out as shown in the diagram and photo, with each queen on a square of its own color.
The pieces are divided, by convention, into white and black sets. The players are referred to as "White" and "Black", and each begins the game with 16 pieces of the specified color. These consist of one king, one queen, two rooks, two bishops, two knights, and eight pawns.

Movement

White always moves first. After the first move, players alternately move one piece per turn (except for castling, when two pieces are moved). Pieces are moved to either an unoccupied square or one occupied by an opponent's piece, which is captured and removed from play. With the sole exception of en passant, all pieces capture by moving to the square that the opponent's piece occupies. A player may not make any move that would put or leave his or her king under attack. A player cannot "pass"; at each turn they have to make a legal move (this is the basis for the finesse called zugzwang). If the player to move has no legal moves, the game is over; it is either a checkmate (a loss for the player with no legal moves) if the king is under attack, or a stalemate (a draw) if the king is not.
Each chess piece has its own style of moving. In the diagrams, the dots mark the squares where the piece can move if no other pieces (including one's own piece) are on the squares between the piece's initial position and its destination.

Moves of a king

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Moves of a rook

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Moves of a bishop

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Moves of a queen

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Moves of a knight

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Moves of a pawn

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

The king moves one square in any direction. The king has also a special move which is called castling and involves also moving a rook.
The rook can move any number of squares along any rank or file, but may not leap over other pieces. Along with the king, the rook is involved during the king's castling move.
The bishop can move any number of squares diagonally, but may not leap over other pieces.
The queen combines the power of the rook and bishop and can move any number of squares along rank, file, or diagonal, but it may not leap over other pieces.
The knight moves to any of the closest squares that are not on the same rank, file, or diagonal, thus the move forms an "L"-shape: two squares vertically and one square horizontally, or two squares horizontally and one square vertically. The knight is the only piece that can leap over other pieces.

The pawn may move forward to the unoccupied square immediately in front of it on the same file, or on its first move it may advance two squares along the same file provided both squares are unoccupied (black "●"s in the diagram); or the pawn may capture an opponent's piece on a square diagonally in front of it on an adjacent file, by moving to that square (black "x"s). The pawn has two special moves: the en passant capture and pawn promotion.

Castling

Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player's first rank^{[note 1]}) and then placing the rook on the last square the king has just crossed. Castling is permissible under the following conditions:^[2]

Neither the king nor the rook may have been previously moved during the game.
There must be no pieces between the king and the rook.
The king may not be in check, nor may the king pass through squares that are under attack by enemy pieces, nor move to a square where it is in check.

En passant

When a pawn advances two squares from its starting position and there is an opponent's pawn on an adjacent file next to its destination square, then the opponent's pawn can capture it en passant (in passing), and move to the square the pawn passed over. However, this can only be done on the very next move, otherwise the right to do so is forfeit. For example, if the black pawn has just advanced two squares from g7 (initial starting position) to g5, then the white pawn on f5 may take it via en passant on g6 (but only on white's next move).

Promotion

When a pawn advances to the eighth rank, as a part of the move it is promoted and must be exchanged for the player's choice of queen, rook, bishop, or knight of the same color. Usually, the pawn is chosen to be promoted to a queen, but in some cases another piece is chosen; this is called underpromotion. In the diagram on the right, the pawn on c7 can be advanced to the eighth rank and be promoted to an allowed piece. There is no restriction placed on the piece that is chosen on promotion, so it is possible to have more pieces of the same type than at the start of the game (for example, two queens).

Check

When a king is under immediate attack by one or two of the opponent's pieces, it is said to be in check. A response to a check is a legal move if it results in a position where the king is no longer under direct attack (that is, not in check). This can involve capturing the checking piece; interposing a piece between the checking piece and the king (which is possible only if the attacking piece is a queen, rook, or bishop and there is a square between it and the king); or moving the king to a square where it is not under attack. Castling is not a permissible response to a check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no legal way to remove it from attack. It is illegal for a player to make a move that would put or leave his own king in check.

End of the game

Win

Although the objective of the game is to checkmate the opponent, chess games do not have to end in checkmate—either player may resign which is a win for the other player.^[4] It is usually considered poor etiquette to play on in a truly hopeless position, and for this reason high level games rarely end with a checkmate. In games with a time control, a player may also lose by running out of time, even with a much superior position.

Draw

Games may end in a draw in several ways:

Draw by agreement - draws are most commonly reached by mutual agreement between the players. The correct procedure is to verbally offer the draw, make a move, then start the opponent's clock. Traditionally players have been allowed to agree a draw at any time in the game, occasionally even without playing a move; in recent years efforts have been made to discourage short draws, for example by forbidding draw offers before move thirty.
Stalemate - the player whose turn it is to move is not in check, but has no legal move.
Threefold repetition of a position - this most commonly occurs when neither side is able to avoid repeating moves without incurring a disadvantage. The three occurrences of the position need not occur on consecutive moves for a claim to be valid. FIDE rules make no mention of perpetual check; this is merely a specific type of draw by threefold repetition.
The fifty-move rule - if during the previous 50 moves no pawn has been moved and no capture has been made, either player may claim a draw; this requires the players to keep a valid written record of the game so that the claim may be verified by the arbiter if challenged. There are in fact several known endgames where it is theoretically possible to force a mate but which require more than 50 moves before the pawn move or capture is made; examples include some endgames with two knights against a pawn and some pawnless endgames such as queen against two bishops. These endings are rare, however, and few players study them in detail, so the fifty-move rule is considered practical for over the board play. Some correspondence chess organisations allow exceptions to the fifty-move rule.^{[note 2]}
Insufficient material - a player may claim a draw if their opponent has insufficient material to checkmate, for example if the player has only the king left and the opponent has only the king and a bishop. Such a claim is only valid if checkmate is impossible.

Time control

Chess games may also be played with a time control, mostly by club and professional players. If a player's time runs out before the game is completed, the game is automatically lost (provided his opponent has enough pieces left to deliver checkmate). The duration of a game ranges from long games played up to seven hours to shorter rapid chess games, usually lasting 30 minutes or one hour per game. Even shorter is blitz chess, with a time control of three to 15 minutes for each player, and bullet chess (under three minutes). In tournament play, time is controlled using a game clock that has two displays, one for each player's remaining time.

Notation for recording moves

Chess games and positions are recorded using a special notation, most often algebraic chess notation.^[6] Abbreviated (or short) algebraic notation generally records moves in the format "abbreviation of the piece moved – file where it moved – rank where it moved". For example, Qg5 means "queen moves to the g-file and 5th rank" (that is, to the square g5). If there are two pieces of the same type that can move to the same square, one more letter or number is added to indicate the file or rank from which the piece moved, e.g. Ngf3 means "knight from the g-file moves to the square f3". The letter P indicating a pawn is not used, so that e4 means "pawn moves to the square e4".
If the piece makes a capture, "x" is inserted before the destination square. Thus Bxf3 means "bishop captures on f3". When a pawn makes a capture, the file from which the pawn departed is used in place of a piece initial, and ranks may be omitted if unambiguous. For example, exd5 (pawn on the e-file captures the piece on d5) or exd (pawn on the e-file captures a piece somewhere on the d-file).

"Scholar's mate"

If a pawn moves to its last rank, achieving promotion, the piece chosen is indicated after the move, for example e1Q or e1=Q. Castling is indicated by the special notations 0-0 for kingside castling and 0-0-0 for queenside castling. An en passant capture is sometimes marked with the notation "e.p." A move that places the opponent's king in check usually has the notation "+" added. (The notation "++" for a double check is considered obsolete). Checkmate can be indicated by "#". At the end of the game, "1–0" means "White won", "0–1" means "Black won", and "½–½" indicates a draw.^[7]
Chess moves can be annotated with punctuation marks and other symbols. For example "!" indicates a good move, "!!" an excellent move, "?" a mistake, "??" a blunder, "!?" an interesting move that may not be best, or "?!" a dubious move not easily refuted.^[8]
For example, one variant of a simple trap known as the Scholar's mate (see animated diagram) can be recorded:

1. e4 e5

2. Qh5?! Nc6

3. Bc4 Nf6??

4. Qxf7# 1–0

Strategy and tactics

Chess strategy consists of setting and achieving long-term positioning advantages during the game – for example, where to place different pieces – while tactics concentrate on immediate maneuver. These two parts of the chess-playing process cannot be completely separated, because strategic goals are mostly achieved through tactics, while the tactical opportunities are based on the previous strategy of play. A game of chess is normally divided into three phases: opening, typically the first 10 moves, when players move their pieces to useful positions for the coming battle; then middlegame; and last the endgame, when most of the pieces are gone, kings typically take a more active part in the struggle, and pawn promotion is often decisive.

Fundamentals of tactics

In chess, tactics in general concentrate on short-term actions – so short-term that they can be calculated in advance by a human player or by a computer. The possible depth of calculation depends on the player's ability. In quiet positions with many possibilities on both sides, a deep calculation is more difficult and may not be practical, while in "tactical" positions with a limited number of forced variations, strong players can calculate long sequences of moves.
Simple one-move or two-move tactical actions – threats, exchanges of material, and double attacks – can be combined into more complicated combinations, sequences of tactical maneuvers that are often forced from the point of view of one or both players.^[10] Theoreticians describe many elementary tactical methods and typical maneuvers; for example, pins, forks, skewers, batteries, discovered attacks (especially discovered checks), zwischenzugs, deflections, decoys, sacrifices, underminings, overloadings, and interferences.^[11]
A forced variation that involves a sacrifice and usually results in a tangible gain is called a combination.^[10] Brilliant combinations – such as those in the Immortal Game – are considered beautiful and are admired by chess lovers. A common type of chess exercise, aimed at developing players' skills, is showing players a position where a decisive combination is available and challenging them to find it.^[12