views/rules/Chess960.pug

   1 p.boxed
   2     | Orthodox rules (with shuffled starting position).
   3
   4 h3 Basics
   5
   6 p.
   7     Chess is played between two players, one moving the white pieces and the other
   8     the black pieces. A "move" consists of a piece's movement on the board.
   9     White and black moves alternate until a specific situation occurs (checkmate,
  10     stalemate, or draw criteria met; this is detailed later).
  11     White pieces always make the first move.
  12
  13 p.
  14     Each piece has a particular way to move, but almost always captures by moving to an
  15     occupied square (with only one exception, detailed later).
  16
  17 figure.diagram-container
  18     .diagram
  19         | fen:rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR:
  20     figcaption Standard initial position.
  21
  22 p.
  23     Board coordinates: squares are always identified by a couple (letter, number).
  24     The letter starts from 'a' and indicates the column, while the number starts
  25     at '1' and indicates the row.
  26     Since the chessboard is 64 squares, 8x8, this results in a coordinates system
  27     from a1 to h8. 'a1' is the bottom left corner square from the white pieces
  28     player perspective, while 'h8' is in the upper right corner.
  29
  30 h3 Regular moves
  31
  32 h4 Pawns
  33
  34 p.
  35     They are the weakest pieces on board, but the most complex to move.
  36     From their initial rank they can either jump two squares forward (vertically),
  37     or advance only one square in this same direction. After that first move they
  38     only advance one square at a time, vertically, moving up.
  39
  40 p.
  41     Pawns capture by moving forward (upper on the board) one square diagonally,
  42     when an enemy piece sits on that square.
  43
  44 p.
  45     When reaching the last rank, pawns must promote into any (friendly)
  46     other non-royal piece: queen, rook, knight or bishop.
  47
  48 p.
  49     Moves notations: "pawn" is implicit, so for a simple move we only write the
  50     destination square (because only one pawn at most can move forward to a specific
  51     square). Thus, 1.e4 means "pawn from e2 to e4". However, in case of captures
  52     the situation could be ambiguous (two pawns on the same rank), so the column
  53     is specified too: "fxe6" (for example).
  54     As you can see capture is marked by a cross symbol: "x".
  55
  56 figure.diagram-container
  57     .diagram
  58         | fen:k7/8/8/1prp4/1P1P4/8/6P1/7K:
  59     figcaption Possible pawn moves: g3, g4, dxc5, bxc5
  60
  61 p
  62     | For a piece movement, we just prepend the upper-case piece initial before the
  63     | previously described notation. A rook taking something on f3 square writes:
  64     | Rxf3. There are rules for ambiguous situation, but discussing them now would
  65     | be too far off-topic. Please visit for example the
  66     a(href="https://en.wikipedia.org/wiki/Algebraic_notation_(chess)")
  67         | Wikipedia page
  68     | for full information on this subject.
  69
  70 h4 Rooks
  71
  72 p.
  73     They move either horizontally or vertically, as far as they want while the path
  74     is free of pieces. If this path ends with an enemy piece, it can a priori be captured
  75     (a priori because if the move ends up with the king in check, then it's illegal).
  76
  77 h4 Knights
  78
  79 p.
  80     They are the only units able to jump over other pieces (without capturing them).
  81     They do "L" moves: two squares in one direction (horizontally or vertically),
  82     and then one square in an orthogonal direction.
  83
  84 figure.diagram-container
  85     .diagram
  86         | fen:k7/2p5/5q2/2b5/4N3/2R3r1/3P4/7K f6,d6,c5,f2,g3,g5:
  87     figcaption Possible knight moves from e4.
  88
  89 h4 Bishops
  90
  91 p.
  92     They move diagonally, as far as they want while the path is free of pieces.
  93     If this path ends with an enemy piece, it can a priori be captured.
  94
  95 h4 Queen
  96
  97 p This piece combines the movement of a rook and a bishop, with the same conditions.
  98
  99 h4 King
 100
 101 p.
 102     This piece moves like a queen, but only by one square at a time. The final square
 103     must be either vacant or occupied by an enemy piece (therefore captured).
 104
 105 p.
 106     The king cannot be captured, but a move may ends up attacking enemy's king.
 107     It is said to be "under check" (or "in check") and the opponent must either:
 108 ul
 109     li move the king to a safe square, or
 110     li capture the attacker, or
 111     li intercept the attacking line.
 112 p Depending on the situation one or more of these counter-measures could be impossible.
 113
 114 p Leaving our king in check after a move is forbidden.
 115
 116 TODO: diagram let king in check capturing queen, bishop pinned
 117 figure.diagram-container
 118     .diagram
 119         | fen:r6k/4q3/8/8/8/B7/8/K7:
 120     figcaption Bxe7 is illegal (it allows Rxa1).
 121
 122 h3 Special moves
 123
 124 p Apart from pawn promotion which has already been introduced, two special moves exist:
 125 ul
 126     li.
 127         castle: if both the king and the right-most (from white player perspective) rook
 128         haven't moved yet, and if nothing stand in the path from king to rook, and if the
 129         squares f1 and g1 are either free or occupied by the king or rook implied, then
 130         the king can go to g1 while the rook moves to f1. Note that since positions are
 131         shuffled one of these two pieces may apparently not move.
 132         The same can be done on the other side (left-most rook), and end squares are c1
 133         for king and d1 for rook. The former is small castle, and the latter large castle.
 134         Notation: small castle writes "0-0" while large castle is "0-0-0".
 135     li.
 136         en-passant: after a pawn has jumped two squares, if an enemy pawn stands just next
 137         to it then it can capture the jumping pawn "en passant", exactly as if it had
 138         advanced only one square. The move is noted as usual, but with "e.p." in the end
 139         to indicate the special move.
 140         The capture is possible only right after the pawn jump: not later in the game.
 141
 142 figure.diagram-container
 143     .diagram2
 144         | fen:nr1kb1r1/ppp3pp/8/2Pp4/8/7P/PP3PP1/1R3KBR:
 145     .diagram2
 146         | fen:nr1kb1r1/ppp3pp/3P4/8/8/7P/PP3PP1/2KR2BR:
 147     figcaption.
 148         Left: black just played d5 (jump from d7).
 149         Right: after cxd6 e.p. and 0-0-0.
 150
 151 h3 End of the game
 152
 153 p.
 154     The best-known way to end a game is by "checkmating" the enemy king.
 155     This means that you end a move in a situation where the king can be captured,
 156     and your opponent has no way to avoid the capture.
 157     The checkmating player has one point and the other zero, so the score writes 1-0
 158     or 0-1 depending if white pieces or black pieces mated.
 159
 160 figure.diagram-container
 161     .diagram
 162         | fen:rnbqkbnr/ppp2Qpp/2np4/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR:
 163     figcaption Famous mating pattern: 1-0
 164
 165 p All other ways to end the game lead to a draw (1/2-1/2): nobody wins:
 166 ul
 167     li when a player has no legal move but is not under check,
 168     li.
 169         when a position is repeated three times with the same castling right and
 170         same player in turn,
 171     li when 50 moves are played without pawn movement or capture.
 172 p.
 173     Note: this last way to end a game is not implemented, because it quite seldom occurs,
 174     does not generalize so well to variants (it depends), and more important because
 175     games played on this website are not official tournament games. If you feel like
 176     manoeuvring for 200 moves and your opponent isn't bored, then why would I stop you?
 177     &#9786;