p.boxed
  | The capture of an enemy piece produces a new "checkered" piece belonging
  | to both players.

figure.showPieces.text-center
  img(src="/images/pieces/Checkered/cp.svg")
  img(src="/images/pieces/Checkered/cr.svg")
  img(src="/images/pieces/Checkered/cn.svg")
  img(src="/images/pieces/Checkered/cb.svg")
  img(src="/images/pieces/Checkered/cq.svg")
  figcaption Checkered pieces, born after captures.

p Note: the initial French name for this variant is "l'Échiqueté".

p The game potentially evolves in two stages.

h2.stageDelimiter Stage 1

h3 Basics

ol
  li
    | Each capture produces a new piece, taking on nature of
    | the capturing or captured one.
  li
    | The new piece arising from a capture has a new color:
    | "checkered", as illustrated above.
  li
    | All checkered pieces belong to the player in turn and can
    | capture the opponents pieces.

p Remarks:
ul
  li.
    A non-capturing checkered move cannot be "undone" right after since
    this would repeat the same position.
  li Checkered pieces cannot be captured.

figure.diagram-container
  .diagram
    | fen:2kr4/pp6/2p5/4ss1r/1P2ns1P/2Np4/P1P1P1BP/R2o1RK1:
  figcaption.
    Black plays Rxh4=P. (Checkered pawn to) h5 is allowed then,
    because piece's nature changed.

h3 Pawns

ul
  li.
    Pawns can jump two squares only from their initial rank, and only once in
    the game. A checkered pawn keeps this right if the starting pawn
    did not use it.
  li.
    Checkered pawns cannot capture en passant, because while the pawn was
    "passing" they were of the same color.

h3 Stalemate or checkmate?

p.
  The following diagram seems to show a mating pattern, but the king if
  "attacked" by a checkered pawn – which still belongs to white.
  Therefore, it can be considered that it's not really a check because
  white is unable to "give back the turn".
  Without the black bishop on a7 it would be mate (without debate), because
  the king could virtually go to g1 before being captured by the
  chameleon pawn.

figure.diagram-container
  .diagram
    | fen:7k/b5pp/8/8/8/8/6ss/7K:
  figcaption After 1...g2+(#?)

p.
  The interface considers that it's mate in both cases, following the idea
  "it's checkmate if we cannot move, and the opponent on its turn could
  take the king" (maybe after an impossible move).

h2.stageDelimiter Stage 2

p.italic.
  This stage can be disabled by unselecting "With switch" at game creation.

p.
  During the game one of the two players can decide to take control of the
  checkered pieces.
  They thus become autonomous and vulnerable to being captured - stage 2
  begins. The other player is in charge of both the white and black pieces, and
  tries to eliminate checkered pieces.
  The checkered side wins by checkmating either the white or black king.

p.
  To take the checkered pieces, play a move that "takes opponent's king" with
  your king, and then execute a move. This is possible only if no such move
  can capture a king.

h4 Variant of stage 2 (unimplemented)
p.
  An observer could decide to join the game by taking the checkered pieces
  at any moment.
  It then becomes a chess game with three players, with some subtelties to be
  resolved. It was tested in some (real life) games organised by the variant
  inventor.

h3 Special moves

p Checkered pawns can...
ul
  li move and capture in either direction;
  li take en passant,
  li be promoted on either the first or eighth row.

h3 Credits

ul
  li.
    The rules of Checkered Chess were thought up by Patrick Bernier and
    developed with the help of Benjamin Auder around 2011-2012.
  li.
    Thanks also to Olive Martin, Christian Poisson, Bevis Martin, Laurent
    Nouhaud and Frédéric Fradet.