我如何让角色在pygame中拖拽相机的边缘？

import pygame

class Camera:
    def __init__(self, width, height):
        self.camera = pygame.Rect(0, 0, width, height)
        self.width = width
        self.height = height

    def update(self, target):
        x = -target.rect.x + int(self.width / 2)
        y = -target.rect.y + int(self.height / 2)

        # 设置相机的移动范围
        x = min(0, x)  # 防止相机超出地图左边界
        y = min(0, y)  # 防止相机超出地图上边界
        x = max(-(self.width - pygame.display.get_surface().get_width()), x)  # 防止相机超出地图右边界
        y = max(-(self.height - pygame.display.get_surface().get_height()), y)  # 防止相机超出地图下边界

        self.camera = pygame.Rect(x, y, self.width, self.height)

def main():
    pygame.init()
    screen_width, screen_height = 800, 600
    screen = pygame.display.set_mode((screen_width, screen_height))
    clock = pygame.time.Clock()
    running = True

    # 创建角色
    player = pygame.Rect(200, 200, 50, 50)
    camera = Camera(screen_width, screen_height)

    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False

        # 监听鼠标移动事件
        mouse_x, mouse_y = pygame.mouse.get_pos()

        # 判断鼠标是否接近相机边缘
        edge_threshold = 20
        if mouse_x < edge_threshold:
            camera.update(player)
            player.x -= 5  # 更新角色位置
        elif mouse_x > screen_width - edge_threshold:
            camera.update(player)
            player.x += 5  # 更新角色位置
        if mouse_y < edge_threshold:
            camera.update(player)
            player.y -= 5  # 更新角色位置
        elif mouse_y > screen_height - edge_threshold:
            camera.update(player)
            player.y += 5  # 更新角色位置

        # 渲染
        screen.fill((255, 255, 255))  # 填充白色背景
        pygame.draw.rect(screen, (255, 0, 0), player)  # 绘制角色矩形
        pygame.display.flip()  # 刷新屏幕

        clock.tick(60)  # 控制帧率

    pygame.quit()

if __name__ == '__main__':
    main()