Special Moves

Pawn Promotion

Pawns are the only piece in chess that can promote. Pawn promotion occurs when the Pawn reaches the end rank of opposite side of the board (1st rank of black, 8th rank of white).

En Passant

En Passant is a special Pawn move. If a Pawn steps forward two squares and landing adjacent to an opponent's Pawn, the opponent's Pawn may capture your Passant and move one square forward.  The En Passant capture is optional, because it only take place after a Pawn moves two squares and only on the move immediately following.

Castling

Castling is a special move to make the King safer. In one turn, the Castling is done by having the king move two squares in the direction of the Rook, and then the Rook crosses over the king and is placed on the square adjacent to the king.[Ref.Figure1& Figure2]

Rules of Castling:
1.The King cannot castle if either the King or the Rook involved have already moved in that round.

2.There can be no pieces between the King and the Rook. 

3.The King cannot castle while in check. [Ref.Figure3]

4.The King cannot castle into or through checkmate.[Ref.Figure4]

5.The King can never "un-castle" after castiling already. 

6.Moving with single hand, King moves firstly and Rook moves secondly.