from machine import Pin, ADC
from utime import sleep
from neopixel import NeoPixel 
num_led = 16

leds = NeoPixel(Pin(18), num_led)
a = 0
pot1 = ADC(Pin(15))
pot2 = ADC(Pin(2))
pot3 = ADC(Pin(0))

while True:
    for i in range(a, num_led):
        leds[i] = (pot1.read()//16, pot2.read()//16, pot3.read()//16)
        leds.write()
        sleep(0.5)
        leds[i] = (0, 0, 0)
        leds.write()

    for i in reversed(range(num_led-1)):
        a = 1
        leds[i] = (pot1.read()//16, pot2.read()//16, pot3.read()//16)
        leds.write()
        sleep(0.5)
        leds[i] = (0, 0, 0)
        leds.write()