def polygon(*points)
      if points.length.zero?
        Kernel.raise ArgumentError, 'no points specified'
      elsif points.length.odd?
        Kernel.raise ArgumentError, 'odd number of points specified'
      end
      primitive 'polygon ' + points.join(',')
    end
def polygon(*points)
      if points.length.zero?
        Kernel.raise ArgumentError, 'no points specified'
      elsif points.length.odd?
        Kernel.raise ArgumentError, 'odd number of points specified'
      end
      primitive 'polygon ' + points.join(',')
    end
Draw a polygon