import pygame
from pygame import locals

# 初始化pygame，为使用硬件做准备
pygame.init()

# 创建一个窗口
screen = pygame.display.set_mode((660, 480))
FPSCLOCK = pygame.time.Clock()  # pygame时钟，控制游戏速度（帧数）

# 背景
background = pygame.image.load('bg.png')
right = pygame.image.load('right.png')      # 头 朝右
food = pygame.image.load('apple.png')       # 食物 苹果
body = pygame.image.load('body.png')        # 身体
left = pygame.image.load('left.png')        # 头 朝左
up = pygame.image.load('up.png')            # 头 朝上
down = pygame.image.load('down.png')        # 头 朝下

x, y = 240, 120
position = [(180, 90), (180, 120), (210, 120), (x, y)]

setheading = "right"
snake_head = right

while True:
    for event in pygame.event.get():
        if event.type == locals.QUIT:
            # 接收到退出事件后退出程序
            exit()
        if event.type == locals.KEYDOWN:
            if event.key == locals.K_RIGHT and setheading != "left":
                setheading = 'right'
                snake_head = right
            if event.key == locals.K_LEFT and setheading != "right":
                setheading = 'left'
                snake_head = left
            if event.key == locals.K_UP and setheading != "down":
                setheading = 'up'
                snake_head = up
            if event.key == locals.K_DOWN and setheading != "up":
                setheading = 'down'
                snake_head = down

    # 设置贪吃蛇的头部坐标
    if setheading == "right":
        x += 30
    elif setheading == "left":
        x -= 30
    elif setheading == "up":
        y -= 30
    else:
        y += 30
    position.append((x, y))
    position.pop(0)
    # 将背景图画上去
    screen.blit(background, (0, 0))
    # 将贪吃蛇的头画上去
    screen.blit(snake_head, position[-1])
    # 将贪吃蛇的身体画上去
    for i in range(len(position)-1):
        screen.blit(body, position[i])

    # 将果实画上去
    screen.blit(food, (360, 300))
    # 刷新画面
    pygame.display.update()
    FPSCLOCK.tick(3)