import pygame
import random

# 初始化 pygame
pygame.init()

# 色彩定義
WHITE = (255, 255, 255)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLACK = (0, 0, 0)

# 螢幕大小
SCREEN_WIDTH = 640
SCREEN_HEIGHT = 480

# 蛇和食物大小
BLOCK_SIZE = 20

# 設定螢幕
screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
pygame.display.set_caption('貪食蛇遊戲')

clock = pygame.time.Clock()

font = pygame.font.SysFont(None, 25)

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

def message(msg, color):
    mesg = font.render(msg, True, color)
    screen.blit(mesg, [SCREEN_WIDTH/6, SCREEN_HEIGHT/3])

def gameLoop():
    game_over = False
    game_close = False

    x1 = SCREEN_WIDTH / 2
    y1 = SCREEN_HEIGHT / 2

    x1_change = 0
    y1_change = 0

    snake_list = []
    snake_length = 1

    foodx = round(random.randrange(0, SCREEN_WIDTH - BLOCK_SIZE) / 10.0) * 10.0
    foody = round(random.randrange(0, SCREEN_HEIGHT - BLOCK_SIZE) / 10.0) * 10.0

    while not game_over:

        while game_close == True:
            screen.fill(WHITE)
            message("你輸了！按 Q 退出或 R 重新開始", RED)
            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_r:
                        gameLoop()

        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:
                    x1_change = -BLOCK_SIZE
                    y1_change = 0
                elif event.key == pygame.K_RIGHT:
                    x1_change = BLOCK_SIZE
                    y1_change = 0
                elif event.key == pygame.K_UP:
                    y1_change = -BLOCK_SIZE
                    x1_change = 0
                elif event.key == pygame.K_DOWN:
                    y1_change = BLOCK_SIZE
                    x1_change = 0

        if x1 >= SCREEN_WIDTH or x1 < 0 or y1 >= SCREEN_HEIGHT or y1 < 0:
            game_close = True
        x1 += x1_change
        y1 += y1_change
        screen.fill(WHITE)
        pygame.draw.rect(screen, RED, [foodx, foody, BLOCK_SIZE, BLOCK_SIZE])
        snake_head = []
        snake_head.append(x1)
        snake_head.append(y1)
        snake_list.append(snake_head)
        if len(snake_list) > snake_length:
            del snake_list[0]

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

        draw_snake(snake_list)
        pygame.display.update()

        if x1 == foodx and y1 == foody:
            foodx = round(random.randrange(0, SCREEN_WIDTH - BLOCK_SIZE) / 10.0) * 10.0
            foody = round(random.randrange(0, SCREEN_HEIGHT - BLOCK_SIZE) / 10.0) * 10.0
            snake_length += 1

        clock.tick(15)

    pygame.quit()
    quit()

gameLoop()
python snake_game.py