// LED PINS
int led_pins[3] = {13,12,11};
int led_pins_length = sizeof(led_pins)/sizeof(led_pins[0]);

// Delay
int anim_delay = 400;

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

void loop() {
  // put your main code here, to run repeatedly:
  for (int i = 0; i < led_pins_length; i++){
    digitalWrite(led_pins[i], HIGH);
    delay(anim_delay);
    digitalWrite(led_pins[i], LOW);
    delay(anim_delay);
  }
}