code: def update_points(self):
          
          n = max(8, min(72, int(2*sqrt(self.r_x+self.r_y))))
          d = pi * 2 / n
          x, y, r_x, r_y = self.x, self.y, self.r_x, self.r_y
  
          ps = []
          for i in range(n):
              ps += [(x + r_x * sin(d * i)), (y + r_y * cos(d * i))]
          self.points = tuple(ps)
docs: 椭圆的近似图形：72边形