"""
Example number: 45

base 10 number system (Decimal)
╭─────┬─────╮
│ 10¹ │ 10⁰ │
├─────┼─────┤
│  4  │  5  │
╰─────┴─────╯
(4 * 10¹) + (5 * 10⁰)
(4 * 10)  + (5 * 1)
 40       +  5        = 45


base 2 number system (Binary)
╭────┬────┬────┬────┬────┬────╮
│ 2⁵ │ 2⁴ │ 2³ │ 2² │ 2¹ │ 2⁰ │
├────┼────┼────┼────┼────┼────┤
│ 1  │ 0  │ 1  │ 1  │ 0  │ 1  │
╰────┴────┴────┴────┴────┴────╯
(1 * 2⁵) + (0 * 2⁴) + (1 * 2³) + (1 * 2²) + (0 * 2¹) + (1 * 2⁰)
(1 * 32) + (0 * 16) + (1 *  8) + (1 *  4) + (0 *  2) + (1 *  1)
 32      +  0       +  8       +  4       +  0       +  1        = 45


base 16 number system (Hexadecimal)
1 = 1, 2 = 2, 3 = 3, ... , A = 10, B = 11, C = 12, D = 13, E = 14, F = 15
╭─────┬─────╮
│ 16¹ │ 16⁰ │
├─────┼─────┤
│  2  │  D  │
╰─────┴─────╯
(4 * 16¹) + (D * 16⁰)
(2 *  16) + (13 * 1)
 32       +  13        = 45
"""

from machine import Pin
from time import sleep

# Assign all LEDs
led1 = Pin(15, Pin.OUT)
led2 = Pin(14, Pin.OUT)
led3 = Pin(13, Pin.OUT)
led4 = Pin(12, Pin.OUT)

WAIT_TIME = 0.4  # time to wait between each sequence
ALL_LEDs = [led4, led3, led2, led1]  # list will all the leds we defined

# main loop
while True:
    for i in range(2 ** len(ALL_LEDs)):  # for every combination...
        binary_num = f'{i:0>4b}' # format number to 4-bit binary string
        print(binary_num)  # print binary number
        
        for j in range(len(binary_num)):  # go through all the binary digits
            if binary_num[j] == '1':  # if it's a 1...
                ALL_LEDs[j].value(1)  # set respective LED on
            else:  # if it's NOT a 1
                ALL_LEDs[j].value(0)  # set respective LED off
        
        sleep(WAIT_TIME)  # wait before flashing the next sequence