chess

Console-based chess game that highlights available moves for the selected piece. To play, run ruby game.rb. Use the arrow keys to move the cursor and the space bar to confirm input. Note: does not implement castling or en passant.

Technical Features

module Slideable
  def moves
    dirs.each_with_object([]) do |(dx, dy), moves|
      x, y = pos

      loop do
        x += dx
        y += dy
        end_pos = [x, y]

        break unless board.in_bounds?(end_pos)

        if board[end_pos].is_a?(NullPiece)
          moves << end_pos
        else
          moves << end_pos if board[end_pos].color != color
          break
        end
      end
    end
  end
end

module Stepable
  def moves
    steps.each_with_object([]) do |(dx, dy), moves|
      x, y = pos
      end_pos = [x + dx, y + dy]

      next unless board.in_bounds?(end_pos)

      if board[end_pos].is_a?(NullPiece) || board[end_pos].color != color
        moves << end_pos
      end
    end
  end
end

Classes for pieces include either the Slideable (Rook, Bishop, Queen) or Stepable (Knight, King) modules, above. The Pawn class is implemented separately:

class Pawn < Piece
  def symbol
    "\u265F"
  end

  def moves
    advance.each_with_object([]) do |(dx, dy), moves|
      x, y = pos
      end_pos = [x + dx, y + dy]

      if board.in_bounds?(end_pos) && board[end_pos].is_a?(NullPiece)
        moves << end_pos
      end
    end + capture.each_with_object([]) do |(dx, dy), moves|
      x, y = pos
      end_pos = [x + dx, y + dy]

      next unless board.in_bounds?(end_pos)
      if !board[end_pos].is_a?(NullPiece) && board[end_pos].color != color
        moves << end_pos
      end
    end
  end

  private

  def advance
    if color == :white
      pos[0] == 6 ? [[-1, 0], [-2, 0]] : [[-1, 0]]
    else
      pos[0] == 1 ? [[1, 0], [2, 0]] : [[1, 0]]
    end
  end

  def capture
    color == :white ? [[-1, -1], [-1, 1]] : [[1, -1], [1, 1]]
  end
end