import pygame
import random
import sys

# 初始化pygame
pygame.init()

# 窗口设置
WIDTH, HEIGHT = 600, 400
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("贪吃蛇游戏")

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

# 蛇方块大小、速度
block_size = 20
speed = 15

# 字体
font = pygame.font.SysFont(None, 35)

# 显示分数
def show_score(score):
    text = font.render(f"得分：{score}", True, WHITE)
    screen.blit(text, [0, 0])

# 绘制蛇
def draw_snake(block_size, snake_list):
    for x in snake_list:
        pygame.draw.rect(screen, GREEN, [x[0], x[1], block_size, block_size])

# 游戏提示文字
def message(msg, color):
    mesg = font.render(msg, True, color)
    screen.blit(mesg, [WIDTH/6, HEIGHT/3])

# 主游戏循环
def game_loop():
    game_over = False
    game_close = False

    # 蛇初始坐标
    x1, y1 = WIDTH/2, HEIGHT/2
    x1_change, y1_change = 0, 0

    # 蛇身体列表
    snake_list = []
    snake_length = 1

    # 随机食物位置
    food_x = round(random.randrange(0, WIDTH - block_size) / block_size) * block_size
    food_y = round(random.randrange(0, HEIGHT - block_size) / block_size) * block_size

    clock = pygame.time.Clock()

    while not game_over:
        # 游戏失败界面
        while game_close:
            screen.fill(BLACK)
            message("游戏结束！按Q退出，按C重新开始", RED)
            show_score(snake_length - 1)
            pygame.display.update()

            for event in pygame.event.get():
                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_q:  # Q退出
                        game_over = True
                        game_close = False
                    if event.key == pygame.K_c:  # C重开
                        game_loop()
                if event.type == pygame.QUIT:
                    game_over = True
                    game_close = False

        # 监听窗口关闭、按键
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                game_over = True
            if event.type == pygame.KEYDOWN:
                # 防止反向直接撞死自己
                if event.key == pygame.K_LEFT and x1_change != block_size:
                    x1_change = -block_size
                    y1_change = 0
                elif event.key == pygame.K_RIGHT and x1_change != -block_size:
                    x1_change = block_size
                    y1_change = 0
                elif event.key == pygame.K_UP and y1_change != block_size:
                    y1_change = -block_size
                    x1_change = 0
                elif event.key == pygame.K_DOWN and y1_change != -block_size:
                    y1_change = block_size
                    x1_change = 0

        # 撞墙判定
        if x1 >= WIDTH or x1 < 0 or y1 >= HEIGHT or y1 < 0:
            game_close = True

        screen.fill(BLACK)
        # 绘制食物
        pygame.draw.rect(screen, RED, [food_x, food_y, block_size, block_size])

        # 更新蛇头坐标
        x1 += x1_change
        y1 += y1_change
        snake_head = [x1, y1]
        snake_list.append(snake_head)

        # 保持长度，移除尾部
        if len(snake_list) > snake_length:
            del snake_list[0]

        # 撞到自己判定
        for seg in snake_list[:-1]:
            if seg == snake_head:
                game_close = True

        draw_snake(block_size, snake_list)
        show_score(snake_length - 1)
        pygame.display.update()

        # 吃到食物，加长蛇、刷新食物
        if x1 == food_x and y1 == food_y:
            food_x = round(random.randrange(0, WIDTH - block_size) / block_size) * block_size
            food_y = round(random.randrange(0, HEIGHT - block_size) / block_size) * block_size
            snake_length += 1

        clock.tick(speed)

    pygame.quit()
    sys.exit()

# 启动游戏
if __name__ == "__main__":
    game_loop()