from machine import Pin
from time import sleep

led1=Pin(0,Pin.OUT)
led2=Pin(1,Pin.OUT)
led3=Pin(2,Pin.OUT)
led4=Pin(3,Pin.OUT)

temp=0
while True:
    temp+=1
    sleep(0.5)
    if temp%2>0:
        led4.on()
    else:
        led4.off()
    if temp%4>1:
        led3.on()
    else:
        led3.off()
    if temp%8>3:
        led2.on()
    else:
        led2.off()
    if temp%16>7:
        led1.on()
    else:
        led1.off()
    
    if temp==15:
        break
    sleep(0.5)