import pygame
import random

pygame.init()

# 设置屏幕大小
screen_width = 800
screen_height = 600
screen = pygame.display.set_mode((screen_width, screen_height))

# 设置标题
pygame.display.set_caption("小游戏")

# 设置颜色
white = (255, 255, 255)
black = (0, 0, 0)

# 设置游戏时钟
clock = pygame.time.Clock()

# 设置字体
font = pygame.font.SysFont(None, 25)

def message_to_screen(msg, color):
    screen_text = font.render(msg, True, color)
    screen.blit(screen_text, [screen_width/2 - screen_text.get_width()/2, screen_height/2 - screen_text.get_height()/2])

def game_loop():
    game_exit = False
    game_over = False

    x = screen_width / 2
    y = screen_height / 2
    x_change = 0
    y_change = 0

    block_size = 10
    speed = 30

    while not game_exit:

        while game_over:
            screen.fill(white)
            message_to_screen("游戏结束，按C重新开始，按Q退出", black)
            pygame.display.update()

            for event in pygame.event.get():
                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_q:
                        game_exit = True
                        game_over = False
                    if event.key == pygame.K_c:
                        game_loop()

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

        if x >= screen_width or x < 0 or y >= screen_height or y < 0:
            game_over = True

        x += x_change
        y += y_change

        screen.fill(white)
        pygame.draw.rect(screen, black, [x, y, block_size, block_size])
        pygame.display.update()

        clock.tick(speed)

    pygame.quit()

game_loop()