如何在pygame中绘制动态箭头？

import pygame
import sys

pygame.init()
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Dynamic Arrow")

arrow_x = 400  # 箭头初始位置
arrow_y = 300
arrow_speed = 5  # 箭头移动速度
arrow_angle = 0  # 箭头初始角度
arrow_length = 50  # 箭头长度

while True:
    screen.fill((255, 255, 255))  # 清空屏幕

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        arrow_x -= arrow_speed
    if keys[pygame.K_RIGHT]:
        arrow_x += arrow_speed
    if keys[pygame.K_UP]:
        arrow_y -= arrow_speed
    if keys[pygame.K_DOWN]:
        arrow_y += arrow_speed

    mouse_pos = pygame.mouse.get_pos()
    dx = mouse_pos[0] - arrow_x
    dy = mouse_pos[1] - arrow_y
    arrow_angle = (180 / pygame.math.pi) * -pygame.math.atan2(dy, dx)

    pygame.draw.polygon(screen, (0, 0, 0), [(arrow_x, arrow_y), (arrow_x - arrow_length, arrow_y + arrow_length/2), (arrow_x - arrow_length, arrow_y - arrow_length/2)])
    rotated_arrow = pygame.transform.rotate(screen, arrow_angle)
    screen.blit(rotated_arrow, (arrow_x, arrow_y))
    pygame.display.flip()

pygame.quit()
sys.exit()