Pygame grid with coords and random numbers

import pygame
import random

pygame.init()
pygame.font.init()

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)


SURFACE_SIZE = (600, 400)
SCREEN = pygame.display.set_mode(SURFACE_SIZE)
FONT = pygame.font.SysFont("arial", size=12)

GRID_SIZE = 4
CELL_SIZE = SURFACE_SIZE[1] // GRID_SIZE
LEFT_MARGIN = (SURFACE_SIZE[0] - CELL_SIZE * GRID_SIZE) // 2

grid = {(x, y) : random.randint(0, 3) for y in range(GRID_SIZE) for x in range(GRID_SIZE)}

quit_demo = False
while not quit_demo:
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.KEYUP:
            if event.key == pygame.K_ESCAPE:
                quit_demo = True

    SCREEN.fill(BLACK)

    for indices, number in grid.items():

        cell_x = LEFT_MARGIN + indices[0] * CELL_SIZE
        cell_y = indices[1] * CELL_SIZE

        pygame.draw.rect(SCREEN, WHITE, (cell_x, cell_y, CELL_SIZE, CELL_SIZE), 1)


        text_surface = FONT.render("({} , {})".format(indices[0], indices[1]), True, WHITE)
        text_size = text_surface.get_rect().size
        SCREEN.blit(text_surface, (cell_x + CELL_SIZE // 2 - text_size[0] // 2, cell_y + CELL_SIZE // 2 - text_size[1]))

        text_surface = FONT.render(str(number), True, WHITE)
        text_size = text_surface.get_rect().size
        SCREEN.blit(text_surface, (cell_x + CELL_SIZE // 2 - text_size[0] // 2, cell_y + CELL_SIZE // 2))

    pygame.display.update()