int wait = 200;
int arr[8] = {13, 12, 11, 10, 9, 8, 7, 6};


void setup() {
  for (int i = 0; i < 8; i++) {
    pinMode(arr[i], OUTPUT);
  }
}


void loop() {
  for (int i = 0; i < 8; i++) {
    digitalWrite(arr[i], HIGH);
    delay(wait);
    digitalWrite(arr[i], LOW);
  }
}