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+p.boxed
+ | You have two new pieces in a pocket, which can appear after any
+ | first piece movement.
+
+p.
+ When a piece is moved for the first time, it is possible to place a new
+ piece at its initial square.
+ You have two pieces that can enter the game like this:
+ul
+ li The Hawk (H): moving like a bishop + knight.
+ li The Elephant (E): moving like a rook + knight.
+
+figure.diagram-container
+ .diagram
+ | fen:rnbqkbnr/pppppppp/8/8/8/2N5/PPPPPPPP/REBQKBNR:
+ figcaption.
+ Position after 1.Nc3/E. White moved his knight from b1 to c3 and placed
+ the elephant on b1.
+
+p.
+ After castling, a new piece can be put at the initial king square
+ (if not occupied), or at the initial rook square - but not both.
+
+p.
+ If a move let the king under check, then it is forbidden,
+ even if placing a pocket piece would have covered the check.
+
+h3 Source
+
+p
+ | Some explanations about the rules and a link to buy a physical S-Chess set
+ | on the
+ a(href="http://www.seirawanchess.com/") Seirawan Chess page
+ | . This variant is playable on
+ a(href="https://www.pychess.org/variant/seirawan") pychess-variants
+ | with an engine available for analysis. See also the
+ a(href="https://en.wikipedia.org/wiki/Seirawan_chess") Wikipedia page
+ | .
+
+p Inventors: Yasser Seirawan and Bruce Harper (2008)