python pygame 小球游戏

# -*- coding:utf-8 -*-
import sys
import pygame


pygame.init()
size = width,height=640,480
screen = pygame.display.set_mode(size)
color = (0,0,0)

ball = pygame.image.load('ball.jpg')
ballrect = ball.get_rect()

speed = [5,5]
clock = pygame.time.Clock()
while True:
    # clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

    ballrect = ballrect.move(speed)
    if ballrect.left < 0 or ballrect.right > width:
        speed[0] = -speed[0]
    if ballrect.top < 0 or ballrect.bottom > height:
        speed[1] = -speed[1]

    screen.fill(color)
    screen.blit(ball,ballrect)
    pygame.display.flip()

pygame.quit()