python flappy bird

dober dan malo se igram in delam nekoč popularno igro flappy bird v pythonu.Ampak ker se naletel na težavo se obračam na vas napaka je zelo banalna ampak dejansko ne vidim napake v kodi.torej namesto da bi se mi pipes(cevi) pojavljale pred mano se z nekega čudnega razloga pojavljajo za mano. kaj mi lahko prosim samo kdo pove ali namigne kje je napaka?

Hvala vsem za odgovore že vnaprej

import pygame
import sys
import random


pygame.init()
WIDTH,HEIGTH=551,720
win=pygame.display.set_mode((WIDTH,HEIGTH))
pygame.display.set_caption("FLAPY BIRDS")
black=(0,0,0)
clock=pygame.time.Clock()

bird_images = [pygame.image.load("assets/bird_down.png"),
               pygame.image.load("assets/bird_mid.png"),
               pygame.image.load("assets/bird_up.png")]
skyline_image = pygame.image.load("assets/background.png")
ground_image = pygame.image.load("assets/ground.png")
top_pipe_image = pygame.image.load("assets/pipe_top.png")
bottom_pipe_image = pygame.image.load("assets/pipe_bottom.png")
game_over_image = pygame.image.load("assets/game_over.png")
start_image = pygame.image.load("assets/start.png")

scrool_speed=1
bird_start_position=(100,250)

class Pipes(pygame.sprite.Sprite):
    def __init__(self,x,y,image):
        pygame.sprite.Sprite.__init__(self)
        self.image=image
        self.rect=self.image.get_rect()
        self.x=x
        self.y=y
    def update(self):
        self.rect.x-=scrool_speed
        if self.rect.x<=- WIDTH:
            self.kill()






class Bird(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image=bird_images[0]
        self.rect=self.image.get_rect()
        self.rect.center=bird_start_position
        self.image_index=0
        self.vel=0
        self.flap=False


    def update(self,user_input):
        self.image_index+=1
        if self.image_index>=30:
            self.image_index=0
        self.image=bird_images[self.image_index//10]

        self.vel+=0.5
        if self.vel>7:
            self.vel=7
        if self.rect.y<500:
            self.rect.y+=int(self.vel)
        if self.vel==0:
            self.flap=False

        self.image=pygame.transform.rotate(self.image,self.vel*-7)
        if user_input[pygame.K_SPACE] and not self.flap and self.rect.y>0:
            self.flap=True
            self.vel=-7

class Ground(pygame.sprite.Sprite):
    def __init__(self,x,y):
        pygame.sprite.Sprite.__init__(self)
        self.image=ground_image
        self.rect=self.image.get_rect()
        self.rect.x,self.rect.y=x,y

    def update(self):
        self.rect.x-=scrool_speed
        if self.rect.x<=-WIDTH:
            self.kill()

def main():

    bird=pygame.sprite.GroupSingle()
    bird.add(Bird())
    pipe_timer=0
    pipes=pygame.sprite.Group()



    x_pos_ground,y_pos_ground=0,520
    ground=pygame.sprite.Group()
    ground.add(Ground(x_pos_ground,y_pos_ground))

    run=True
    FPS=60
    while run:

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



        win.blit(skyline_image,(0,0))
        if len(ground)<=2:
            ground.add(Ground(WIDTH, y_pos_ground))
        usr = pygame.key.get_pressed() 


        pipes.draw(win)
        ground.draw(win)
        bird.draw(win)

        pipes.update()
        ground.update()
        bird.update(usr)

        if pipe_timer<=0:
            x_top,x_bottom=550,550
            y_top=random.randint(-600, -480)
            y_bottom=y_top+random.randint(90,130)+bottom_pipe_image.get_height()
            pipes.add(Pipes(x_top,y_top,top_pipe_image))
            pipes.add(Pipes(x_bottom,y_bottom,bottom_pipe_image))
            pipe_timer=random.randint(180,250)
        pipe_timer-=1

        clock.tick(FPS)
        pygame.display.update()

if __name__ == '__main__':
    main()