import sys
import random
import pygame
from pygame.locals import *
 
# 目標方塊的顏色 紅色
redColor = pygame.Color(255, 0, 0)
# 游戲界面的背景顏色 純黑色
blackColor = pygame.Color(0, 0, 0)
# 貪吃蛇的顏色 白色
whiteColor = pygame.Color(255, 255, 255)
 
 
# 定義游戲結束的函數
def gameOver():
  pygame.quit()
  sys.exit()
 
 
# 定義main函數
def main():
  # 初始化pygame
  pygame.init()
  # 定義一個控制速度的函數
  fpsClock = pygame.time.Clock()
  # 創建顯示層
  playSurface = pygame.display.set_mode((640,480))  # 界面的大小
  pygame.display.set_caption('貪吃蛇')
  # 初始化蛇的位置
  snake_position=[100,100]
 
  # 初始化蛇的長度
  snake_body = [[100,100],[80,100],[60,100]]
 
  # 初始化目標方塊的位置
  target_position = [300,300]
 
  # 目標方塊的狀態
  target_flag = 1
 
  # 初始化一個方向
  direction = 'right'
  # 定義蛇的方向變量
  changeDirection = direction
 
  while True:
    # pygame的交互模塊和事件隊列
    for event in pygame.event.get():
      # 是否推出
      if event.type == QUIT:
        pygame.quit()
        sys.exit()
      # 判斷鍵盤事件
      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))
 
    # 根據鍵盤反應確定方向
    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
 
 
    # 根據方向移動蛇頭的坐標
    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
 
    # 蛇與自身的碰撞檢測
    for body in snake_body:
      if snake_position[0] == body[0] and snake_position[1] == body[1]:
        gameOver()
 
    # 蛇移動
    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:
      # 如果沒吃到，蛇尾彈出棧
      snake_body.pop()
 
    # 如果吃掉目標方塊，重新生成一個目標方塊
    if target_flag == 0:
      x = random.randrange(1,32)
      y = random.randrange(1,24)
      # 20*20的像素為一個小矩形
      target_position = [int(x*20),int(y*20)]
      target_flag = 1
 
    # 繪制顯示層
    playSurface.fill(blackColor)
 
    # 繪制蛇
    for position in snake_body:
      pygame.draw.rect(playSurface, redColor, Rect(position[0],position[1],20,20))
 
    # 畫目標方塊
    pygame.draw.rect(playSurface, whiteColor, Rect(target_position[0], target_position[1], 20, 20))
 
    pygame.display.flip()
 
    # 判斷死亡
    if snake_position[0] > 620 or snake_position[1] < 0:
      gameOver()
    elif snake_position[1] > 460 or snake_position[1] < 0:
      gameOver()
 
    # 控制游戲的速度
    fpsClock.tick(5)
 
if __name__ == '__main__':
  main()