import pygame
import random
import sys

pygame.init()

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

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)
GREEN = (0, 255, 0)

BLOCK_SIZE = 20
SPEED = 5

clock = pygame.time.Clock()
# =========修复点：不用SysFont(None,...)，使用内置字体文件=========
font = pygame.font.Font(pygame.font.get_default_font(), 35)


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


def game_loop():
    game_over = False
    game_close = False

    x, y = WIDTH / 2, HEIGHT / 2
    x_change, y_change = 0, 0

    snake_list = []
    snake_length = 1

    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

    while not game_over:
        while game_close:
            screen.fill(BLACK)
            msg1 = font.render("游戏结束！按Q退出，C重新开始", True, RED)
            screen.blit(msg1, [40, HEIGHT / 2])
            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:
                        game_over = True
                        game_close = False
                    if event.key == pygame.K_c:
                        game_loop()
                if event.type == pygame.QUIT:
                    game_over = True
                    game_close = False

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                game_over = True
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT and x_change != BLOCK_SIZE:
                    x_change = -BLOCK_SIZE
                    y_change = 0
                elif event.key == pygame.K_RIGHT and x_change != -BLOCK_SIZE:
                    x_change = BLOCK_SIZE
                    y_change = 0
                elif event.key == pygame.K_UP and y_change != BLOCK_SIZE:
                    y_change = -BLOCK_SIZE
                    x_change = 0
                elif event.key == pygame.K_DOWN and y_change != -BLOCK_SIZE:
                    y_change = BLOCK_SIZE
                    x_change = 0

        if x >= WIDTH or x < 0 or y >= HEIGHT or y < 0:
            game_close = True

        x += x_change
        y += y_change
        screen.fill(BLACK)

        pygame.draw.rect(screen, RED, [food_x, food_y, BLOCK_SIZE, BLOCK_SIZE])

        snake_head = [x, y]
        snake_list.append(snake_head)
        if len(snake_list) > snake_length:
            del snake_list[0]

        for seg in snake_list[:-1]:
            if seg == snake_head:
                game_close = True

        for seg in snake_list:
            pygame.draw.rect(screen, GREEN, [seg[0], seg[1], BLOCK_SIZE, BLOCK_SIZE])

        show_score(snake_length - 1)
        pygame.display.update()

        if x == food_x and y == 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()


if __name__ == "__main__":
    game_loop()