如何在pygame中让形状在屏幕上循环显示？

import pygame
import sys

pygame.init()

screen_width = 800
screen_height = 600
bg_color = (255, 255, 255)  # 白色背景
screen = pygame.display.set_mode((screen_width, screen_height))
screen.fill(bg_color)

rect_width = 50
rect_height = 50
rect_color = (255, 0, 0)  # 红色矩形
rect = pygame.Rect(0, 0, rect_width, rect_height)

rect_x = 0
rect_y = 0
rect_speed = 1

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

    # 更新形状的位置
    rect_x += rect_speed
    if rect_x > screen_width:
        rect_x = 0

    # 在屏幕上绘制形状
    screen.fill(bg_color)
    pygame.draw.rect(screen, rect_color, (rect_x, rect_y, rect_width, rect_height))
    pygame.display.flip()