Pygame -在pygame窗口周围移动一个方块，但在改变方向时无法停止当前的移动，导致方块沿对角线移动。

import pygame
import sys

# 初始化pygame
pygame.init()

# 设置窗口尺寸
size = width, height = 800, 600
screen = pygame.display.set_mode(size)

# 设置方块的初始位置和速度
block_pos = [width // 2, height // 2]
block_speed = [0, 0]

# 游戏主循环
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        # 检测按键事件
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                block_speed[0] = -1  # 向左移动
                block_speed[1] = 0   # 停止垂直移动
            elif event.key == pygame.K_RIGHT:
                block_speed[0] = 1   # 向右移动
                block_speed[1] = 0   # 停止垂直移动
            elif event.key == pygame.K_UP:
                block_speed[0] = 0   # 停止水平移动
                block_speed[1] = -1  # 向上移动
            elif event.key == pygame.K_DOWN:
                block_speed[0] = 0   # 停止水平移动
                block_speed[1] = 1   # 向下移动

    # 更新方块的位置
    block_pos[0] += block_speed[0]
    block_pos[1] += block_speed[1]

    # 绘制方块
    screen.fill((0, 0, 0))
    pygame.draw.rect(screen, (255, 255, 255), pygame.Rect(block_pos[0], block_pos[1], 50, 50))

    # 更新屏幕
    pygame.display.flip()