the same color throughout the game. The queen may move any number of squares vertically, horizontally, or diagonally without jumping. The king may move to any adjoining square. No move may be made such that the king is placed or left in check. The king may participate in castling, which is a move consisting of the king moving two squares toward a same-colored rook on the same rank and the rook moving to the square crossed by the king. Castling may only be performed if the king and rook involved are unmoved, if the king is not in check, if the king would not travel through or into check, and if there are no pieces between the rook and the king. The knight moves from one corner of any two-by-three rectangle to the opposite corner. Consequently, the knight alternates its square color each time it moves. It is not obstructed by other pieces. The pawn may move forward one square, and one or two squares when on its starting square, toward the opponent's side of the board. When there is an enemy piece one square diagonally ahead of a pawn, then the pawn may capture that piece. A pawn can perform a special type of capture of an enemy pawn called en passant ("in passing"), wherein it captures a horizontally adjacent enemy pawn that has just advanced two squares as if that pawn had only advanced one square. If the pawn reaches a square on the of the opponent, it promotes to the player's choice of a queen, rook, bishop, or knight of the same color. Pieces other than pawns capture in the same way that they move. A capturing piece replaces the opponent piece on its square, except for an en passant capture by a pawn. Captured pieces are immediately removed from the game. A square may hold only one piece at any given time. Except for castling and the knight's move, no piece may jump over another piece. Relative value The value assigned to a piece attempts to represent the potential strength of the piece in the game. As the game develops, the relative values of the pieces will also change. For example, in an , bishops are relatively more valuable; they can be positioned to control long, open diagonal spaces. In a with lines of protected pawns blocking bishops, however, knights usually become relatively more potent. Similar