import pygame
import random

WIDTH = 500
HEIGHT = 500
FPS = 25

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))
clock = pygame.time.Clock()

speedY = 0
speedX = 0
running = True
state = []
for index in range(0,400,1):
 state.append(1)

index = 0
indexY = 475
while running:
    
    clock.tick(FPS)
    
    for event in pygame.event.get():
        
        if event.type == pygame.QUIT:
            running = False
                
    
    screen.fill(BLACK)
    counter = 0
    for it_1 in range(0,500,25):
     for it_2 in range(0,500,25):
      if (state[counter]==1):
         pygame.draw.rect(screen,WHITE, (it_1,it_2,24,24))
      if (state[counter]==2):
         pygame.draw.rect(screen,RED, (it_1,it_2,24,24))
      
      counter = counter + 1 
       
    pygame.draw.rect(screen,RED, (speedX,speedY,24,24))
    pygame.display.flip()
    speedY = speedY + 25
    
    if speedY > indexY:
     state[19*index +(index-1) + (20-index)] = 2
     speedY = 0
     speedX = speedX + 25
     index = index + 1
     indexY = indexY - 25
     
     
    if (indexY == -25): 
     indexY = 475
     speedX = 0
    if (index == 20): index = 0
pygame.quit()