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2 | Orthodox rules (with shuffled starting position).
3
4h3 Basics
5
6p.
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
13p.
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
17figure.diagram-container
18 .diagram
19 | fen:rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR:
20 figcaption Standard initial position.
21
22p.
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
30h3 Regular moves
31
32h4 Pawns
33
34p.
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
40p.
41 Pawns capture by moving forward (upper on the board) one square diagonally,
42 when an enemy piece sits on that square.
43
44p.
45 When reaching the last rank, pawns must promote into any (friendly)
46 other non-royal piece: queen, rook, knight or bishop.
47
48p.
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
56figure.diagram-container
57 .diagram
58 | fen:k7/8/8/1prp4/1P1P4/8/6P1/7K:
59 figcaption Possible pawn moves: g3, g4, dxc5, bxc5
60
61p
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
70h4 Rooks
71
72p.
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
77h4 Knights
78
79p.
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
84figure.diagram-container
85 .diagram
da06a6eb 86 | fen:k7/2p5/5q2/2b5/4N3/2R3r1/3P4/7K f6,d6,c5,f2,g3,g5:
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87 figcaption Possible knight moves from e4.
88
89h4 Bishops
90
91p.
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
95h4 Queen
96
97p This piece combines the movement of a rook and a bishop, with the same conditions.
98
99h4 King
100
101p.
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
105p.
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:
108ul
109 li move the king to a safe square, or
110 li capture the attacker, or
111 li intercept the attacking line.
112p Depending on the situation one or more of these counter-measures could be impossible.
113
114p Leaving our king in check after a move is forbidden.
115
116TODO: diagram let king in check capturing queen, bishop pinned
117figure.diagram-container
118 .diagram
119 | fen:r6k/4q3/8/8/8/B7/8/K7:
120 figcaption Bxe7 is illegal (it allows Rxa1).
121
122h3 Special moves
123
124p Apart from pawn promotion which has already been introduced, two special moves exist:
125ul
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
142figure.diagram-container
18f9c763 143 .diagram2
2316f8b8 144 | fen:nr1kb1r1/ppp3pp/8/2Pp4/8/7P/PP3PP1/1R3KBR:
18f9c763 145 .diagram2
2316f8b8 146 | fen:nr1kb1r1/ppp3pp/3P4/8/8/7P/PP3PP1/2KR2BR:
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147 figcaption.
148 Left: black just played d5 (jump from d7).
149 Right: after cxd6 e.p. and 0-0-0.
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150
151h3 End of the game
152
153p.
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
160figure.diagram-container
161 .diagram
162 | fen:rnbqkbnr/ppp2Qpp/2np4/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR:
163 figcaption Famous mating pattern: 1-0
164
165p All other ways to end the game lead to a draw (1/2-1/2): nobody wins:
166ul
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.
172p.
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 ☺