Проблема со змейкой на Pygame

# -*- coding: utf-8 -*-
import pygame
import random
 
pygame.init()
WINDOW_WIDTH = 500
WINDOW_HEIGHT = 500
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)
WINDOW = pygame.display.set_mode((WINDOW_WIDTH, WINDOW_HEIGHT))
pygame.display.set_caption('Astral NT Inc.')
def display_text(text, size, color, x, y):
    font = pygame.font.Font(None, size)
    text_surface = font.render(text, True, color)
    text_rect = text_surface.get_rect()
    text_rect.center = (x, y)
    WINDOW.blit(text_surface, text_rect)
def game_menu():
    menu_running = True
    while menu_running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_RETURN:
                    menu_running = False
        WINDOW.fill(BLACK)
        display_text('Змейка', 80, GREEN, WINDOW_WIDTH // 2, WINDOW_HEIGHT // 4)
        display_text('Нажмите Enter, чтобы начать', 30, WHITE, WINDOW_WIDTH // 2, WINDOW_HEIGHT // 2)
        pygame.display.update()
def game_over():
    over_running = True
 
    while over_running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_RETURN:
                    over_running = False
        WINDOW.fill(BLACK)
        display_text('Game Over!', 80, RED, WINDOW_WIDTH // 2, WINDOW_HEIGHT // 4)
        display_text('Нажмите Enter, чтобы играть снова', 30, WHITE, WINDOW_WIDTH // 2, WINDOW_HEIGHT // 2)
        pygame.display.update()
 
 
def main():
    running = True
    snake_position = [250, 250]
    snake_body = [[250, 250], [240, 250], [230, 250]]
    food_position = [random.randrange(1, 50) * 10, random.randrange(1, 50) * 10]
    food_spawned = True
    direction = 'RIGHT'
    change_direction = direction
    game_menu()
 
    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT and direction != 'RIGHT':
                    change_direction = 'LEFT'
                elif event.key == pygame.K_RIGHT and direction != 'LEFT':
                    change_direction = 'RIGHT'
                elif event.key == pygame.K_UP and direction != 'DOWN':
                    change_direction = 'UP'
                elif event.key == pygame.K_DOWN and direction != 'UP':
                    change_direction = 'DOWN'
        direction = change_direction
        if direction == 'RIGHT':
            snake_position[0] += 10
        elif direction == 'LEFT':
            snake_position[0] -= 10
        elif direction == 'UP':
            snake_position[1] -= 10
        elif direction == 'DOWN':
            snake_position[1] += 10
        snake_body.insert(0, list(snake_position))
        if snake_position == food_position:
            food_spawned = False
        else:
            snake_body.pop()
        if not food_spawned:
            food_position = [random.randrange(1,50)*10,random.randrange(1,50)*10]
            food_spawned = True
 
        WINDOW.fill(BLACK)
        for position in snake_body:
            pygame.draw.rect(WINDOW, GREEN, pygame.Rect(position[0], position[1], 10, 10))
        pygame.draw.rect(WINDOW, RED, pygame.Rect(food_position[0], food_position[1], 10, 10))
        pygame.display.update()
 
        if snake_position[0] < 0 or snake_position[0] > WINDOW_WIDTH-10 or snake_position[1] < 0 or snake_position[1] > WINDOW_HEIGHT-10:
            game_over()
 
        for block in snake_body[1:]:
            if snake_position == block:
                game_over()
 
        pygame.time.Clock().tick(20)
 
    pygame.quit()
    quit()
 
if __name__ == '__main__':
    main()