from microbit import *
from random import *

group_a = pin0
group_b = pin1 
group_c = pin2

min = 100
max = 1023


def fade(pin):
    interval = randint(min, max) / 20

    brightness = 5
    for i in range(20):

        brightness += interval
        pin.write_analog(brightness)

        sleep(50)

    for i in range(20):

        brightness -= interval

        pin.write_analog(brightness)

        sleep(50)


pins = [group_a, group_b, group_c]



while True:
    fade(choice(pins))