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


void setup() {
  // put your setup code here, to run once:
  for (int led = 0; led < NbrLEDs; led++) {
    pinMode(ledPins[led], OUTPUT);
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i = 0; i < NbrLEDs + 1; i++) {
    digitalWrite(ledPins[i], HIGH);
    //delay(1000);
    digitalWrite(ledPins[i - 1], LOW);
    delay(wait_time);
  }

}