title: Draw a transparent rectangles and polygons in pygame
body: <p>How can I draw a rectangle that has a color with an alpha? 
  I have:</p>
  
  <pre><code>windowSurface = pygame.display.set_mode((1000, 750), pygame.DOUBLEBUF)
  pygame.draw.rect(windowSurface, pygame.Color(255, 255, 255, 128), pygame.Rect(0, 0, 1000, 750))
  </code></pre>
  
  <p>But I want the white rectangle to be 50% transparent, but the alpha value doesn't appear to be working.</p>