+ | Orthodox rules (with shuffled starting position).
+
+h3 Basics
+
+p.
+ Chess is played between two players, one moving the white pieces and the other
+ the black pieces. A "move" consists of a piece's movement on the board.
+ White and black moves alternate until a specific situation occurs (checkmate,
+ stalemate, or draw criteria met; this is detailed later).
+ White pieces always make the first move.
+
+p.
+ Each piece has a particular way to move, but almost always captures by moving to an
+ occupied square (with only one exception, detailed later).
+
+figure.diagram-container
+ .diagram
+ | fen:rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR:
+ figcaption Standard initial position.
+
+p.
+ Board coordinates: squares are always identified by a couple (letter, number).
+ The letter starts from 'a' and indicates the column, while the number starts
+ at '1' and indicates the row.
+ Since the chessboard is 64 squares, 8x8, this results in a coordinates system
+ from a1 to h8. 'a1' is the bottom left corner square from the white pieces
+ player perspective, while 'h8' is in the upper right corner.
+
+h3 Regular moves
+
+h4 Pawns
+
+p.
+ They are the weakest pieces on board, but the most complex to move.
+ From their initial rank they can either jump two squares forward (vertically),
+ or advance only one square in this same direction. After that first move they
+ only advance one square at a time, vertically, moving up.
+
+p.
+ Pawns capture by moving forward (upper on the board) one square diagonally,
+ when an enemy piece sits on that square.
+
+p.
+ When reaching the last rank, pawns must promote into any (friendly)
+ other non-royal piece: queen, rook, knight or bishop.
+
+p.
+ Moves notations: "pawn" is implicit, so for a simple move we only write the
+ destination square (because only one pawn at most can move forward to a specific
+ square). Thus, 1.e4 means "pawn from e2 to e4". However, in case of captures
+ the situation could be ambiguous (two pawns on the same rank), so the column
+ is specified too: "fxe6" (for example).
+ As you can see capture is marked by a cross symbol: "x".
+
+figure.diagram-container
+ .diagram
+ | fen:k7/8/8/1prp4/1P1P4/8/6P1/7K:
+ figcaption Possible pawn moves: g3, g4, dxc5, bxc5
+
+p
+ | For a piece movement, we just prepend the upper-case piece initial before the
+ | previously described notation. A rook taking something on f3 square writes:
+ | Rxf3. There are rules for ambiguous situation, but discussing them now would
+ | be too far off-topic. Please visit for example the
+ a(href="https://en.wikipedia.org/wiki/Algebraic_notation_(chess)")
+ | Wikipedia page
+ | for full information on this subject.
+
+h4 Rooks
+
+p.
+ They move either horizontally or vertically, as far as they want while the path
+ is free of pieces. If this path ends with an enemy piece, it can a priori be captured
+ (a priori because if the move ends up with the king in check, then it's illegal).
+
+h4 Knights
+
+p.
+ They are the only units able to jump over other pieces (without capturing them).
+ They do "L" moves: two squares in one direction (horizontally or vertically),
+ and then one square in an orthogonal direction.
+
+figure.diagram-container
+ .diagram
+ | fen:k7/2p5/5q2/2b5/4N3/2R3r1/3P4/7K w f6,d6,c5,f2,g3,g5:
+ figcaption Possible knight moves from e4.
+
+h4 Bishops
+
+p.
+ They move diagonally, as far as they want while the path is free of pieces.
+ If this path ends with an enemy piece, it can a priori be captured.
+
+h4 Queen
+
+p This piece combines the movement of a rook and a bishop, with the same conditions.
+
+h4 King
+
+p.
+ This piece moves like a queen, but only by one square at a time. The final square
+ must be either vacant or occupied by an enemy piece (therefore captured).
+
+p.
+ The king cannot be captured, but a move may ends up attacking enemy's king.
+ It is said to be "under check" (or "in check") and the opponent must either:
+ul
+ li move the king to a safe square, or
+ li capture the attacker, or
+ li intercept the attacking line.
+p Depending on the situation one or more of these counter-measures could be impossible.
+
+p Leaving our king in check after a move is forbidden.
+
+TODO: diagram let king in check capturing queen, bishop pinned
+figure.diagram-container
+ .diagram
+ | fen:r6k/4q3/8/8/8/B7/8/K7:
+ figcaption Bxe7 is illegal (it allows Rxa1).
+
+h3 Special moves
+
+p Apart from pawn promotion which has already been introduced, two special moves exist:
+ul
+ li.
+ castle: if both the king and the right-most (from white player perspective) rook
+ haven't moved yet, and if nothing stand in the path from king to rook, and if the
+ squares f1 and g1 are either free or occupied by the king or rook implied, then
+ the king can go to g1 while the rook moves to f1. Note that since positions are
+ shuffled one of these two pieces may apparently not move.
+ The same can be done on the other side (left-most rook), and end squares are c1
+ for king and d1 for rook. The former is small castle, and the latter large castle.
+ Notation: small castle writes "0-0" while large castle is "0-0-0".
+ li.
+ en-passant: after a pawn has jumped two squares, if an enemy pawn stands just next
+ to it then it can capture the jumping pawn "en passant", exactly as if it had
+ advanced only one square. The move is noted as usual, but with "e.p." in the end
+ to indicate the special move.
+ The capture is possible only right after the pawn jump: not later in the game.
+
+figure.diagram-container
+ .diagram
+ | fen:nr1kb1r1/ppp3pp/8/2Pp4/8/7P/PP3PP1/1R3KBR:
+ figcaption Black just played d5 (jump from d7).
+
+figure.diagram-container
+ .diagram
+ | fen:nr1kb1r1/ppp3pp/3P4/8/8/7P/PP3PP1/2KR2BR:
+ figcaption After cxd6 e.p. and 0-0-0.
+
+h3 End of the game
+
+p.
+ The best-known way to end a game is by "checkmating" the enemy king.
+ This means that you end a move in a situation where the king can be captured,
+ and your opponent has no way to avoid the capture.
+ The checkmating player has one point and the other zero, so the score writes 1-0
+ or 0-1 depending if white pieces or black pieces mated.
+
+figure.diagram-container
+ .diagram
+ | fen:rnbqkbnr/ppp2Qpp/2np4/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR:
+ figcaption Famous mating pattern: 1-0
+
+p All other ways to end the game lead to a draw (1/2-1/2): nobody wins:
+ul
+ li when a player has no legal move but is not under check,
+ li.
+ when a position is repeated three times with the same castling right and
+ same player in turn,
+ li when 50 moves are played without pawn movement or capture.
+p.
+ Note: this last way to end a game is not implemented, because it quite seldom occurs,
+ does not generalize so well to variants (it depends), and more important because
+ games played on this website are not official tournament games. If you feel like
+ manoeuvring for 200 moves and your opponent isn't bored, then why would I stop you?
+ ☺
projects / vchess.git / commitdiff