// Black Led Test

#define NUM_LEDS 12

int blackLedPins[NUM_LEDS] = {13,12,11,10,9,8,7,6,5,4,3,2};

int direction = +1;
int position = 0;

void setup() 
{
  for( auto a:blackLedPins)
    pinMode(a, OUTPUT);
}

void loop() 
{
  digitalWrite(blackLedPins[position],HIGH);
  delay(150);
  digitalWrite(blackLedPins[position],LOW);
  position += direction;
  if(position == NUM_LEDS - 1 or position == 0)
    direction = -direction;
}