title: Enemy character is being overdrawn by game's background
body: <p>I am working on a game which spawns enemies. Though once these enemies are spawned, they instantly disappear again because the background is drawn on top of them.</p>
  
  <p>Is there a way to have a layer system in Pygame?</p>
  
  <p><strong>Code to recreate the problem:</strong></p>
  
  <pre><code>import pygame
  import threading
  from random import randint
  from time import sleep
  
  pygame.init()
  window = pygame.display.set_mode((900, 900))
  bg=pygame.image.load("Background.png").convert()
  
  def Gameplay():
      while True:  
          window.blit(bg, [0,0])
          pygame.display.update()
  
  def spawn_enemy():
      enemyW = 50
      enemyH = 50
      enemyX = 420
      enemyY = 850
      pygame.draw.rect(window, (93,124,249),(enemyX,enemyY,enemyW, enemyH))
      print("an enemy has been spawned")
      return True # would be "return enemy" after you create your enemy entity
  
  def EnemySpawn():
      enemy_list = [] # to maintain records of all enemies made
      while True: # make enemies forever
          sleep(randint(1,5))
          enemy_list.append(spawn_enemy()) # call our function we made above which spawns enemies
  
  Gameplay = threading.Thread(target=Gameplay)
  Gameplay.start()
  EnemySpawn = threading.Thread(target=EnemySpawn)
  EnemySpawn.start()
  </code></pre>