请你编写一段代码，功能是实现贪吃蛇小游戏

好的，以下是一个简单的 Python 贪吃蛇小游戏代码：

import pygame
import random

# 初始化游戏
pygame.init()

# 定义游戏画面大小
WIDTH, HEIGHT = 640, 480
screen = pygame.display.set_mode((WIDTH, HEIGHT))

# 定义颜色
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)

# 设置游戏标题
pygame.display.set_caption("贪吃蛇游戏")

# 定义蛇的初始位置和大小
snake_pos = [100, 50]
snake_body = [[100, 50], [90, 50], [80, 50]]

# 定义食物的初始位置
food_pos = [random.randrange(1, (WIDTH//10)) * 10, random.randrange(1, (HEIGHT//10)) * 10]
food_spawn = True

# 定义蛇的移动方向
direction = "RIGHT"
change_to = direction

# 定义蛇的移动速度
snake_speed = 10

# 定义游戏结束的函数
def game_over():
    font_style = pygame.font.SysFont(None, 50)
    message = font_style.render("Game Over", True, RED)
    screen.blit(message, [WIDTH/2 - 100, HEIGHT/2 - 50])
    pygame.display.update()
    pygame.time.delay(2000)
    pygame.quit()
    quit()

# 游戏循环
while True:
    # 处理游戏事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_RIGHT:
                change_to = "RIGHT"
            elif event.key == pygame.K_LEFT:
                change_to = "LEFT"
            elif event.key == pygame.K_UP:
                change_to = "UP"
            elif event.key == pygame.K_DOWN:
                change_to = "DOWN"

    # 判断蛇是否吃到食物
    if snake_pos == food_pos:
        food_spawn = False
    else:
        snake_body.pop()

    # 生成新的食物
    if not food_spawn:
        food_pos = [random.randrange(1, (WIDTH//10)) * 10, random.randrange(1, (HEIGHT//10)) * 10]
        food_spawn = True

    # 移动蛇的位置
    if change_to == "RIGHT" and direction != "LEFT":
        direction = "RIGHT"
    elif change_to == "LEFT" and direction != "RIGHT":
        direction = "LEFT"
    elif change_to == "UP" and direction != "DOWN":
        direction = "UP"
    elif change_to == "DOWN" and direction != "UP":
        direction = "DOWN"

    if direction == "RIGHT":
        snake_pos[0] += snake_speed
    elif direction == "LEFT":
        snake_pos[0] -= snake_speed
    elif direction == "UP":
        snake_pos[1] -= snake_speed
    elif direction == "DOWN":
        snake_pos[1] += snake_speed

    # 更新蛇的身体
    snake_body.insert(0, list(snake_pos))

    # 判断游戏是否结束
    if snake_pos[0] < 0 or snake_pos[0] > WIDTH-10:
        game_over()
    elif snake_pos[1] < 0 or snake_pos[1] > HEIGHT-10:
        game_over()
    for block in snake_body[1:]:
        if snake_pos == block:
            game_over()

    # 绘制游戏画面
    screen.fill(BLACK)
    pygame.draw.rect(screen, GREEN, [food_pos[0], food_pos[1], 10, 10])
    for block in snake_body:
        pygame.draw.rect(screen, WHITE, [block[0], block[1], 10, 10])

    pygame.display.update()

这段代码用 Pygame 库实现了贪吃蛇小游戏，玩家可以通过方向键控制蛇的移动方向。游戏的规则是让蛇吃到食物，每吃到一个食物就会增加一个身体块，蛇不能碰到墙壁或自己的身体，否则游戏结束。