# File lib/bangkok/piece.rb, line 143
  def could_perform_move(move)
    return false unless super

    square = move.square
    d_file = (@square.file - square.file).abs
    d_rank = (@square.rank - square.rank).abs
    return (d_file == 2 && d_rank == 1) || (d_file == 1 && d_rank == 2)
  end