import pygame
import sys

pygame.init()
screen = pygame.display.set_mode((400, 300))

surface = pygame.surface((50, 50))
surface.fill((0,255,0))

while True:
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        screen.blit()