import pygame, sys
from random import randint

screen = pygame.display.set_mode((640,460))
cuadrados = [ ]
x, y = 0,0

while True:
    for evento in pygame.event.get():
        if evento.type == pygame.MOUSEMOTION:
            x, y = evento.pos
        if evento.type == pygame.MOUSEBUTTONDOWN:
            cuadrados.append((x-5,y-5))
        if evento.type == pygame.KEYDOWN and evento.key == pygame.K_q:
            sys.exit()

    screen.fill((0,0,0))
    for caja in cuadrados:
        color = (randint(0,255), randint(0,255), randint(0,255))
        pygame.draw.rect(screen, color, (caja, (10,10)))
    pygame.draw.rect(screen, (255,255,255), ((x-5,y-5), (10,10)))
    pygame.display.flip()