python- floated little turtle

A little turtle floating around in the back immediately after hitting the wall

 1 import pygame
 2 import sys
 3 
 4 pygame.init()
 5 size = width, height =600, 600
 6 speed = [-2, 1]
 7 bg = (254, 254, 254)
 8 screen = pygame.display.set_mode(size)
 9 pygame.display.set_caption("python小乌龟")
10 turtle =pygame.image.load("turtle.png")
11 position = turtle.get_rect()
12 while True:
13     for event in pygame.event.get(): 
14         if event.type == pygame.QUIT:
15             sys.exit()
16     position = position.move(speed)
17     if position.left < 0 or position.right > width:
18         turtle = pygame.transform.flip(turtle,True,False)
19         speed[0] = -speed[0]
20     if position.top < 0 or position.bottom >height:
21         speed[1] = -speed[-1]
22     screen.fill(bg)
23     screen.blit(turtle,position)
24     pygame.display.flip()
25     pygame.time.delay(10)
26     

The effect is as follows: