# En Passant
When a pawn advances two squares from its original square and ends the turn
adjacent to a pawn of the opponent's on the same rank, it may be captured by
that pawn of the opponent's, as if it had moved only one square forward. This
capture is only legal on the opponent's next move immediately following the
first pawn's advance. The diagrams below demonstrate an instance of this:
if the white pawn moves from a2 to a4, the black pawn on b4 can capture it en passant,
moving from b4 to a3 while the white pawn on a4 is removed from the board.
