1 #!/usr/bin/python
   2 
   3 import sys
   4 from random import randint
   5 import pygame
   6 from pygame.locals import *
   7 
   8 pygame.init()
   9 
  10 class Ball(pygame.sprite.Sprite):
  11       def __init__(self):
  12           pygame.sprite.Sprite.__init__(self)
  13 
  14           self.image = pygame.image.load("ball%d.png" % randint(0,4))
  15           self.image = self.image.convert_alpha()
  16 
  17           self.rect = self.image.get_rect()
  18           self.rect = self.rect.move(randint(self.rect.width, 640-self.rect.width),
  19                                      randint(self.rect.height,480-self.rect.height))
  20 
  21           self.x_speed = randint(1,6)
  22           self.y_speed = randint(1,6)
  23 
  24       def update(self):
  25           width, height = 640, 480
  26 
  27           if self.rect.left < 0 or self.rect.right > width:
  28               self.x_speed = -self.x_speed
  29 
  30           if self.rect.top < 0 or self.rect.bottom > height:
  31               self.y_speed = -self.y_speed
  32 
  33           self.rect = self.rect.move(self.x_speed, self.y_speed)
  34 
  35 
  36 screen = pygame.display.set_mode((640,480))
  37 background = pygame.image.load("sfondo.png").convert()
  38 screen.blit(background,(0,0))
  39 pygame.display.update()
  40 
  41 group = pygame.sprite.RenderUpdates([Ball() for x in range(randint(4,10))])
  42 
  43 while True:
  44      for event in pygame.event.get():
  45          if event.type in (QUIT, KEYDOWN): sys.exit()
  46 
  47      group.clear(screen,background)
  48      group.update()
  49      pygame.display.update(group.draw(screen))
  50 
  51      pygame.time.delay(25)