import pygame
import time

size = 600
pygame.display.init()
screen = pygame.display.set_mode ( ( size, size ) )

for i in range ( 0, size, 25 ):
  pygame.draw.line ( screen, ( 0, 250, 0 ), ( 0, i ), ( i, size ), 1 )
  pygame.draw.line ( screen, ( 0, 250, 0 ), ( i, 0 ), ( size, i ), 1 )
  pygame.draw.line ( screen, ( 0, 250, 0 ), ( size - i, 0 ), ( 0, i ), 1 )
  pygame.draw.line 
reen, ( 0, 250, 0 ), ( i, size ), ( size, size - i ), 1 )
  #time.sleep ( .5 )
  #pygame.display.flip()
pygame.display.flip()

raw_input()
pygame.quit()