gistfile1.rb

  def render
    print " "
    (0..7).each { |column_num| print  " #{column_num} " }
    puts ""
    board.each_with_index do |row, row_num|
      print row_num
      row.each_with_index do |piece, col_num|
        if invalid_board_moves.include?([row_num, col_num])
          print (piece ? piece.render : "   ").colorize(background: :white)
        else
          print (piece ? piece.render : "   ").colorize(background: :blue)
        end
      end
      puts "\n"
    end
  end