Отображение окна в pygame

Подскажите, как побороть. При запуске приложения, вместо background отображается черное окно. При закрытие приложения, на пол секунды появляется background

import pygame

pygame.init()
x = 6
y = 440
width = 50
height = 37
speed = 5
isJump = False
jumpCount = 10
    
left = False
right = False
animationCount = 0
    
window = pygame.display.set_mode((512, 256))
pygame.display.set_caption('Firts Game')
clock = pygame.time.Clock()
    
walkRight = [pygame.image.load('assets\player-run-right-01.png'),
                 pygame.image.load('assets\player-run-right-02.png'), pygame.image.load('assets\player-run-right-03.png'),
                 pygame.image.load('assets\player-run-right-04.png'), pygame.image.load('assets\player-run-right-05.png')]
walkLeft = [pygame.image.load('assets\player-run-left-01.png'),
                pygame.image.load('assets\player-run-left-02.png'), pygame.image.load('assets\player-run-left-03.png'),
                pygame.image.load('assets\player-run-left-04.png'), pygame.image.load('assets\player-run-left-05.png')]
                
background = pygame.image.load('assets\background.png')
playerStand = pygame.image.load('assets\adventurer-idle-03.png')
    
    
def drawWindow():
    global animationCount
    
    window.blit(background, (0, 0))
    
    if animationCount >= 25:
        animationCount = 0
  
    if left:
        window.blit(walkLeft[animationCount // 5], (x, y))
        animationCount += 1
    elif right:
        window.blit(walkRight[animationCount // 5], (x, y))
        animationCount += 1
    else:
        window.blit(playerStand, (x, y))
    
    pygame.display.update()
    
    
run = True
while run:
    clock.tick(25)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT] and x > 5:
        x -= speed
        left = True
        right = False
    elif keys[pygame.K_RIGHT] and x < 500 - width - 5:
        x += speed
        left = False
        right = True
    else:
        left = False
        right = False
        animationCount = 0

    if not(isJump):
        if keys[pygame.K_SPACE]:
            isJump = True
    else:
        if jumpCount >= -10:
            y -= jumpCount * 2
            jumpCount -= 1
        else:
            isJump = False
            jumpCount = 10

    drawWindow()
    
pygame.quit()