import sys
import random
import pygame
from pygame.locals import *
 
# 目标方块的颜色 红色
redColor = pygame.Color(255, 0, 0)
# 游戏界面的背景颜色 纯黑色
blackColor = pygame.Color(0, 0, 0)
# 贪吃蛇的颜色 白色
whiteColor = pygame.Color(255, 255, 255)
 
 
# 定义游戏结束的函数
def gameOver():
  pygame.quit()
  sys.exit()
 
 
# 定义main函数
def main():
  # 初始化pygame
  pygame.init()
  # 定义一个控制速度的函数
  fpsClock = pygame.time.Clock()
  # 创建显示层
  playSurface = pygame.display.set_mode((640,480))  # 界面的大小
  pygame.display.set_caption('贪吃蛇')
  # 初始化蛇的位置
  snake_position=[100,100]
 
  # 初始化蛇的长度
  snake_body = [[100,100],[80,100],[60,100]]
 
  # 初始化目标方块的位置
  target_position = [300,300]
 
  # 目标方块的状态
  target_flag = 1
 
  # 初始化一个方向
  direction = 'right'
  # 定义蛇的方向变量
  changeDirection = direction
 
  while True:
    # pygame的交互模块和事件队列
    for event in pygame.event.get():
      # 是否推出
      if event.type == QUIT:
        pygame.quit()
        sys.exit()
      # 判断键盘事件
      elif event.type == KEYDOWN:
        if event.key == K_RIGHT:
          changeDirection = 'right'
        if event.key == K_LEFT:
          changeDirection = 'left'
        if event.key == K_UP:
          changeDirection = 'up'
        if event.key == K_DOWN:
          changeDirection = 'down'
        if event.key == K_SPACE:
          pygame.event.post(pygame.event.Event(QUIT))
 
    # 根据键盘反应确定方向
    if changeDirection == 'left' and not direction == 'right':
      direction = changeDirection
 
    if changeDirection == 'right' and not direction == 'left':
      direction = changeDirection
 
    if changeDirection == 'up' and not direction == 'down':
      direction = changeDirection
 
    if changeDirection == 'down' and not direction == 'up':
      direction = changeDirection
 
 
    # 根据方向移动蛇头的坐标
    if direction == 'right':
      snake_position[0] += 20
 
    if direction == 'left':
      snake_position[0] -= 20
 
    if direction == 'up':
      snake_position[1] -= 20
 
    if direction == 'down':
      snake_position[1] += 20
 
    # 蛇与自身的碰撞检测
    for body in snake_body:
      if snake_position[0] == body[0] and snake_position[1] == body[1]:
        gameOver()
 
    # 蛇移动
    snake_body.insert(0,list(snake_position))
 
 
 
    if snake_position[0] == target_position[0] and snake_position[1] == target_position[1]:
      target_flag = 0
    else:
      # 如果没吃到，蛇尾弹出栈
      snake_body.pop()
 
    # 如果吃掉目标方块，重新生成一个目标方块
    if target_flag == 0:
      x = random.randrange(1,32)
      y = random.randrange(1,24)
      # 20*20的像素为一个小矩形
      target_position = [int(x*20),int(y*20)]
      target_flag = 1
 
    # 绘制显示层
    playSurface.fill(blackColor)
 
    # 绘制蛇
    for position in snake_body:
      pygame.draw.rect(playSurface, redColor, Rect(position[0],position[1],20,20))
 
    # 画目标方块
    pygame.draw.rect(playSurface, whiteColor, Rect(target_position[0], target_position[1], 20, 20))
 
    pygame.display.flip()
 
    # 判断死亡
    if snake_position[0] > 620 or snake_position[1] < 0:
      gameOver()
    elif snake_position[1] > 460 or snake_position[1] < 0:
      gameOver()
 
    # 控制游戏的速度
    fpsClock.tick(5)
 
if __name__ == '__main__':
  main()