snake_movement_2.rb

  def change_direction(direction)
    @direction = direction
    case direction
      when :up
        @direction_x = 0
        @direction_y = -1
      when :down
        @direction_x = 0
        @direction_y = 1
      when :left
        @direction_x = -1
        @direction_y = 0
      when :right
        @direction_x = 1
        @direction_y = 0
     end
  end