import pygame
import random

WIDTH = 500
HEIGHT = 500
FPS = 60

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)

pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))

running = True
while running:
    
    for event in pygame.event.get():
        
        if event.type == pygame.QUIT:
            running = False
   
    
    screen.fill(WHITE)
    for it_1 in range(0,500,25):
     for it_2 in range(0,500,25):
      pygame.draw.rect(screen,RED, (it_1,it_2,20,20))

    pygame.display.update()
    
pygame.quit()