from machine import Pin
import time
red=Pin(0,Pin.OUT)
blue=Pin(1,Pin.OUT)
green=Pin(2,Pin.OUT)
yellow=Pin(3,Pin.OUT)


x=[red, blue , green, yellow]
j=4
while True:
   for i in range(j):
      x[i].value(1)
      time.sleep(2)
      x[i].value(0)
      time.sleep(2)
   x[j-1].value(1)
   j-=1
   if j==-1:
      j=4
      for k in range(4):
         x[k].value(0)