old_contents: 
  
  import pygame
  
  from settings import Settings
  from ship import Ship
  import game_functions as gf
  
  from pygame.sprite import Group
  
  def run_game():
      # Initialize pygame, settings, and screen object.
      pygame.init()
      ai_settings = Settings()
      screen = pygame.display.set_mode(
          (ai_settings.screen_width, ai_settings.screen_height))
      pygame.display.set_caption("Alien Invasion")
  
      # Make a ship.
      ship = Ship(ai_settings, screen)
      # Make a group to store bullets in.
      bullets = Group()
  
      # Start the main loop for the game.
      while True:
          gf.check_events(ai_settings, screen, ship, bullets)
          ship.update()
          bullets.update()
          gf.update_screen(ai_settings, screen, ship, bullets)
  
  
  run_game()
  
new_contents: 
  
  import pygame
  
  from settings import Settings
  from ship import Ship
  import game_functions as gf
  
  from pygame.sprite import Group
  
  def run_game():
      # Initialize pygame, settings, and screen object.
      pygame.init()
      ai_settings = Settings()
      screen = pygame.display.set_mode(
          (ai_settings.screen_width, ai_settings.screen_height))
      pygame.display.set_caption("Alien Invasion")
  
      # Make a ship.
      ship = Ship(ai_settings, screen)
      # Make a group to store bullets in.
      bullets = Group()
  
      # Start the main loop for the game.
      while True:
          gf.check_events(ai_settings, screen, ship, bullets)
          ship.update()
          bullets.update()
          for bullet in bullets.copy():
              if bullet.rect.bottom <= 0:
                  bullets.remove(bullet)
          print(len(bullets))
  
          gf.update_screen(ai_settings, screen, ship, bullets)
  
  
  run_game()
  
subject: remove bullet out screen