Chess

I am an absolutely huge chess geek. You can look up my USCF profile on www.uschess.org and search for Wu, Theodore L.

How to Play

1. Make sure you have Ruby installed. Check out this [tutorial] (www.installrails.com).
2. Fire up the terminal and open the chess repository.
3. Install the 'colorize' gem.
4. Type in: $ ruby chess.rb . And you are ready to play.

Basic Concepts

Multi-level class inheritance and DRY code facilitates the process for

• Highlighting a piece's valid moves
  
• Handling a variety of errors, such as an illegal move, a move in check, or not-your-turn move.
  
• Storing captured pieces
  

The Cooler Stuff: Building out the AI

• If the King is in check...
  • For the first move that gets the computer out of check, move there. Don't move the king unless you absolutely have to.

  if @board.check?(:black)
    move_king_at_last_resort = []
    @board.pieces(:black).each do |piece|
      piece.moves.each do |move|
        dup_board = @board.dup
        dup_board.move!(piece.position, move)
        unless (dup_board.check?(:black))
          if piece.is_a?(King)
            move_king_at_last_resort = [piece.position,move]
          else
            return [piece.position,move]
          end
        end
      end
    end
    move_king_at_last_resort
  

• Are there any pieces to capture?
  • If there is more than one piece to capture, capture the piece with the highest value. Pawn = 1; Knight/Bishop = 3; Rook = 5; Queen = 10;

  @board.pieces(:black).each do |piece|
    piece.moves.each do |move|
      point_value = 0
      current_piece = @board[move]
      unless current_piece.is_a?(EmptyPiece) && current_piece.color == :white
        if current_piece.is_a?(Pawn)
          point_value = 1
        elsif current_piece.is_a?(Knight) || current_piece.is_a?(Bishop)
          point_value = 3
        elsif current_piece.is_a?(Rook)
          point_value = 5
        elsif current_piece.is_a?(Queen)
          point_value = 10
        end
  

• If there are no pieces to capture...
  • Move the piece that gets you closest to the king.

  king_pos = @board.find_king(:white)
  closest_to = nil
  closest_diff = 0
  
  @board.pieces(:black).each do |piece|
    piece.moves.each do |move|
      if closest_to.nil?
        closest_to = [piece.position, move]
        closest_diff = (king_pos[0] - move[0]).abs + (king_pos[1] - move[1]).abs
        break
      end
      change = (king_pos[0] - move[0]).abs + (king_pos[1] - move[1]).abs
      if change < closest_diff
        closest_diff = change
        closest_to = [piece.position, move]
      end
    end
  end
  

Features to be Implemented

• Add another layer for the AI to think two steps head
• Write a method for the AI to determine checkmate game-winning move
• Add en passant.