我的代码在球从上边界和下边界反弹后不工作，并且没有像预期的那样返回到中心0,0

import pygame
import sys

# 初始化Pygame
pygame.init()

# 设置窗口大小
width, height = 800, 600
screen = pygame.display.set_mode((width, height))
pygame.display.set_caption("Ball Bounce")

# 球的初始位置和速度
ball_pos = [width//2, height//2]
ball_speed = [5, 5]
ball_radius = 20

# 游戏循环
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    # 更新球的位置
    ball_pos[0] += ball_speed[0]
    ball_pos[1] += ball_speed[1]

    # 边界检测和速度更新
    if ball_pos[0] - ball_radius <= 0 or ball_pos[0] + ball_radius >= width:
        ball_speed[0] = -ball_speed[0]
    if ball_pos[1] - ball_radius <= 0 or ball_pos[1] + ball_radius >= height:
        ball_speed[1] = -ball_speed[1]

    # 清屏
    screen.fill((255, 255, 255))

    # 绘制球
    pygame.draw.circle(screen, (255, 0, 0), ball_pos, ball_radius)

    # 更新显示
    pygame.display.flip()

    # 控制帧率
    pygame.time.Clock().tick(60)