如何在Pygame中插入滑块？

import pygame

# 初始化Pygame
pygame.init()

# 设置窗口大小
screen = pygame.display.set_mode((400, 300))
pygame.display.set_caption("Pygame Slider Example")

# 颜色定义
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)

# 滑块参数
slider_pos = [50, 150]
slider_size = [300, 20]
slider_value = 0.5
slider_dragging = False

# 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 slider_pos[0] <= event.pos[0] <= slider_pos[0] + slider_size[0] and \
               slider_pos[1] <= event.pos[1] <= slider_pos[1] + slider_size[1]:
                slider_dragging = True
        elif event.type == pygame.MOUSEBUTTONUP:
            slider_dragging = False
        elif event.type == pygame.MOUSEMOTION:
            if slider_dragging:
                slider_value = (event.pos[0] - slider_pos[0]) / slider_size[0]
                slider_value = max(0, min(1, slider_value))

    # 绘制背景
    screen.fill(WHITE)

    # 绘制滑块
    pygame.draw.rect(screen, BLACK, (slider_pos[0], slider_pos[1], slider_size[0], slider_size[1]), 2)
    pygame.draw.rect(screen, BLACK, (slider_pos[0] + slider_value * slider_size[0] - 5, slider_pos[1] - 5, 10, 30))

    # 更新屏幕
    pygame.display.flip()

# 退出Pygame
pygame.quit()