# binaire teller, op en neer
from machine import Pin
from time import sleep
sleep(0.1) # Wait for USB to become ready

print("Hello, Pi Pico!")
pauze = .5

led0 = Pin(15, Pin.OUT)
led1 = Pin(14, Pin.OUT)
led2 = Pin(13, Pin.OUT)
led3 = Pin(12, Pin.OUT)

l = []
l1 = []

def licht():
    led0.value(int(l[0]))
    led1.value(int(l[1]))
    led2.value(int(l[2]))
    led3.value(int(l[3]))
    sleep(pauze)

b = 0
e = 16
s = 1

while True:
    for i in range(b,e,s):
        l1 = []
        l = list(str(bin(i))[2:])
        if len(l) < 4:
            for x in range(4 -len(l)):
                l1.append('0')    
        l = l1 +l
        licht()
    x = b
    b = e
    e = x
    s = -1 * s
    if s < 0: b = b -1