import pygame

pygame.init()
screen = pygame.display.set_mode((640,480))
running = True

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        else:
            pygame.draw.lines(screen, pygame.color.Color(255,0,0), True, [(20, 20), (20, 100), (100, 100), (100, 20)])
            pygame.display.flip()
pygame.quit()