title: Pygame sceen.fill() not filling up the color properly
body: <p>I've just started learning Pygame . I'm following <a href="https://lorenzod8n.wordpress.com/2007/05/25/pygame-tutorial-1-getting-started/" rel="noreferrer">this</a> tutorial. 
  I ran the following program but it shows black color instead of blue :</p>
  
  <pre><code>import pygame
  
  h = input("Enter the height of the window : ")
  w = input("Enter the width of the window : ")
  screen = pygame.display.set_mode((w,h))
  
  running = True
  while running:
      event = pygame.event.poll()
      if event.type == pygame.QUIT:
          running=0
  
  screen.fill((0,0,1))
  pygame.display.flip()
  </code></pre>