如何让pygame.MOUSEBUTTONDOWN在每次点击时只转一次？

import pygame

# 游戏初始化
pygame.init()

# 创建游戏窗口
window_width, window_height = 800, 600
window = pygame.display.set_mode((window_width, window_height))
pygame.display.set_caption("My Game")

# 定义标志位
mouse_clicked = False

# 游戏主循环
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONDOWN:
            if not mouse_clicked:
                # 执行点击操作
                print("Mouse button clicked")
                mouse_clicked = True
        elif event.type == pygame.MOUSEBUTTONUP:
            mouse_clicked = False

    # 渲染游戏界面
    window.fill((255, 255, 255))
    pygame.display.flip()

# 退出游戏
pygame.quit()