pygame.erreur: système de vidéo n'est pas initialisé

Je ne semble pas capable de se débarrasser de cette erreur quand j'essaie d'exister le jeu. le jeu fonctionne bien mais seulement obtenir l'erreur quand j'essaie d'exister le jeu.

import pygame
from pygame import *
import random
import time
import os
import sys
from pygame.locals import *
black = (0,0,0)
white = (255,255,255)
pygame.init()
def game():
os.environ['SDL_VIDEO_CENTERED'] = '1'
mouse.set_visible(False)
#screen
screen_width = 800
screen_height = 500
screen = pygame.display.set_mode([screen_width,screen_height])
#load images etc.
backdrop = pygame.image.load('bg.jpg').convert_alpha()
menu = pygame.image.load('green.jpg').convert_alpha()
ballpic = pygame.image.load('ball.gif').convert_alpha()
mouseball = pygame.image.load('mouseball.gif').convert_alpha()
display.set_caption('Twerk')
back = pygame.Surface(screen.get_size())
def text(text,x_pos,color,font2=28):
tfont = pygame.font.Font(None, font2)
text=tfont.render(text, True, color)
textpos = text.get_rect(centerx=back.get_width()/2)
textpos.top = x_pos
screen.blit(text, textpos)
start = False
repeat = False
while start == False:
for event in pygame.event.get():
if event.type == pygame.QUIT:
start = True
#falling = True
#finish = True
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_SPACE:
start = True
#game over screen
screen.blit(menu,[0,0])
pygame.display.set_caption("TWERK")
#Text
#"Welcome to Escape"
#needs replacing with logo 
text("Twerk",60,white,300)
#"Instructions"
text("Instructions",310,white)
text("----------------------------------------------------------------------------------------",320,white)
text("Avoid the the enemies",340,white)
text("Last as long as you can!",360,white)
text("Press space to start",420,white)
pygame.display.flip()
while start == True:
positionx=[]
positiony=[]
positionxmove=[]
positionymove=[]
falling = False
finish = False
score=0
enemies=4
velocity=1
for i in range(enemies):
positionx.append(random.randint(300,400)+random.randint(-300,200))
positiony.append(random.randint(200,340)+random.randint(-200,100))
positionxmove.append(random.randint(1,velocity))
positionymove.append(random.randint(1,velocity))
font = pygame.font.Font(None, 28)
text = font.render('Starting Twerk... ', True, (100,100,100))
textRect = text.get_rect()
textRect.centerx = screen.get_rect().centerx
textRect.centery = screen.get_rect().centery
screen.blit(backdrop, (0,0))
screen.blit(text, textRect)
pygame.display.update()
game=time.localtime()
while start == True:
end=time.localtime()
score= (end[1]-game[1])*3600 + (end[4]-game[4])*60 + end[5]-game[5]
if score > 1: break
first=True
strtTime=time.localtime()
while not finish or falling:
screen.blit(backdrop, (0,0))
for i in range(enemies):
screen.blit(ballpic,(positionx[i],positiony[i]))
(mousex,mousey)=mouse.get_pos()
screen.blit(mouseball,(mousex,mousey))
display.update()
strt = time.localtime()
if first:
while True:
end=time.localtime()
score= (end[3]-strt[3])*3600 + (end[4]-strt[4])*60 + end[5]-strt[5]
if score > 3: break
first = False
if falling:
for i in range(enemies):
positionymove[i]=1000
positionxmove[i]=0
for i in range(enemies): positionx[i]=positionx[i]+positionxmove[i]
for i in range(enemies): positiony[i]=min(600,positiony[i]+positionymove[i])
if falling:
falling=False
for posy in positiony:
if posy<600: falling=True
if not falling:
for i in range(enemies):
for j in range(i+1,enemies):
if abs(positionx[i]-positionx[j])<20 and abs(positiony[i]-positiony[j])<20:
temp=positionxmove[i]
positionxmove[i]=positionxmove[j]
positionxmove[j]=temp
temp=positionymove[i]
positionymove[i]=positionymove[j]
positionymove[j]=temp
for i in range(enemies):  
if positionx[i]>600: positionxmove[i]*=-1
if positionx[i]<0: positionxmove[i]*=-1
if positiony[i]>440: positionymove[i]*=-1
if positiony[i]<0: positionymove[i]*=-1
for i in range(enemies):
if abs(positionx[i]-mousex)<40 and abs(positiony[i]-mousey)<40:
falling = True
finish = True
#start = False
endTime=time.localtime()
score= (endTime[3]-strtTime[3])*3600 + (endTime[4]-strtTime[4])*60 + endTime[5]-strtTime[5]
break
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
pygame.quit()
game()

C'est l'erreur que je reçois, j'ai changé quit() pour ARRÊTER, mais toujours pas de chance.

Traceback (most recent call last):
File "C:\Users\MO\Desktop\Twerk\ballbounce_changed.py", line 171, in <module>
game()
File "C:\Users\MO\Desktop\Twerk\ballbounce_changed.py", line 160, in game
for event in pygame.event.get():
pygame.error: video system not initialized

merci 🙂