如何在pygame中让相机跟随自上而下的汽车

import pygame
pygame.init()

screen_width = 800
screen_height = 600
screen = pygame.display.set_mode((screen_width, screen_height))

class Camera:
    def __init__(self, target):
        self.target = target
        self.offset_x = 0
        self.offset_y = 0

    def update(self):
        self.offset_x = self.target.rect.centerx - screen_width // 2
        self.offset_y = self.target.rect.centery - screen_height // 2

class Car(pygame.sprite.Sprite):
    def __init__(self, x, y):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 100))
        self.image.fill((255, 0, 0))
        self.rect = self.image.get_rect()
        self.rect.center = (x, y)
        self.speed = 5

    def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_UP]:
            self.rect.y -= self.speed
        if keys[pygame.K_DOWN]:
            self.rect.y += self.speed

car = Car(screen_width // 2, screen_height // 2)
camera = Camera(car)
all_sprites = pygame.sprite.Group()
all_sprites.add(car)

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

    all_sprites.update()
    camera.update()

    screen.fill((0, 0, 0))
    for sprite in all_sprites:
        screen.blit(sprite.image, (sprite.rect.x - camera.offset_x, sprite.rect.y - camera.offset_y))

    pygame.display.flip()

pygame.quit()