python pygame 공 대작 전 실현

from random import randint,randrange
import pygame
from math import sqrt,pi


class Ball(object):
  def __init__(self, center, color, radius, sx, sy):
    self._center = center
    self._color = color
    self._radius = radius
    self._sx = sx
    self._sy = sy

  @property
  def center(self):
    return self._center

  @property
  def radius(self):
    return self._radius

  @radius.setter
  def radius(self,radius):
    self._radius = radius

  def move(self):
    x, y = self._center[0], self._center[1]
    x += self._sx
    y += self._sy
    self._center = (x, y)
    # if x + self._radius > 800:
    #   self._sx = -abs(self._sx)
    # elif x + self._radius < 0:
    #   self._sx = abs(self._sx)
    # elif y +self._radius > 800:
    #   self._sy = -abs(self._sy)
    # elif y +self._radius < 0:
    #   self._sy = abs(self._sy)
    if x + self._radius >= 800 or x - self._radius <= 0 or x <= 0:
      self._sx = -self._sx
    if y +self._radius >= 800 or y - self._radius <= 0 or y <= 0:
      self._sy = -self._sy

  def draw(self,screen):
    pygame.draw.circle(screen, self._color, self._center, self._radius, 0)

  def eat(self, other):
    a = sqrt((self._center[0] - other.center[0]) ** 2 + (self._center[1] - other.center[1]) ** 2)
    if a < self._radius + other.radius and self._radius < other.radius:
      other.radius = self._radius + other.radius
      self.radius = 0
    elif a < self._radius + other.radius and self._radius > other.radius:
      self._radius = self._radius + other.radius
      other.radius = 0


def main():
  balls = []
  pygame.init()
  screen = pygame.display.set_mode([800,800])
  pygame.display.set_caption('     ')
  c = pygame.time.Clock()
  running = True
  while running:
    for event in pygame.event.get():
      if event.type == pygame.QUIT:
        running = False
      elif event.type == pygame.MOUSEBUTTONDOWN and \
         event.button == 1:
        color = random_color()
        radius = randint(10,100)
        sx, sy = randint(-10,10), randint(-10,10)
        ball = Ball(event.pos, color, radius, sx, sy)
        balls.append(ball)
    refresh(screen,balls)
    c.tick(20) # 50 
    for ball in balls:
      ball.move()
    balls_len = len(balls)
    for i in range(balls_len):
      for x in range(balls_len):
        balls[i].eat(balls[x])
    for ball in balls:
      if ball.radius == 0:
        balls.remove(ball)


  pygame.quit()


def refresh(screen,balls):
  bg_color = [255, 255, 255]
  screen.fill(bg_color)
  for ball in balls:
    ball.draw(screen)
  pygame.display.flip()


def random_color():
  return [randint(1,255), randint(1,255), randint(1,255)]


if __name__ == '__main__':
  main()