const int NbrLEDs = 13;
const int ledPins[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
int wait_time = 30;
#define LED_ON LOW
#define LED_OFF HIGH

void setup()
{
  for (int led = 0; led < NbrLEDs; led++)
  {
    pinMode(ledPins[led], OUTPUT);
  }
}
void loop()
{

  for (int led = 0; led < NbrLEDs - 1; led++)
  {
    digitalWrite(ledPins[led], LED_ON);
    delay(wait_time);
    digitalWrite(ledPins[led + 1], LED_ON);
    delay(wait_time);
    digitalWrite(ledPins[led], LED_OFF);
    delay(wait_time * 2);
  }
  for (int led = NbrLEDs - 1; led > 0; led--)
  {
    digitalWrite(ledPins[led], LED_ON);
    delay(wait_time);
    digitalWrite(ledPins[led - 1], LED_ON);
    delay(wait_time);
    digitalWrite(ledPins[led], LED_OFF);
    delay(wait_time * 2);
  }


}