const int leds[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
const int numLeds = sizeof(leds) / sizeof(leds[0]);
int delayTime = 150;

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

void loop() {
    for (int i = 0; i < numLeds; i++) {
        digitalWrite(leds[i], HIGH);
        delay(delayTime);
        digitalWrite(leds[i], LOW);
    }
}