// knight rider led with 3 leds glowing at a time

const int numLEDs = 12;
const int ledPins[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
const int glowCount = 2;
const int delayTime = 100;

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

void loop() {
  // Forward chase
  for (int i = 0; i <= numLEDs - glowCount; i++) {
    for (int j = 0; j < glowCount; j++) {
      digitalWrite(ledPins[i + j], HIGH);
    }
    delay(delayTime);
    for (int j = 0; j < glowCount; j++) {
      digitalWrite(ledPins[i + j], LOW);
    }
  }

  // Reverse chase
  for (int i = numLEDs - glowCount; i >= 0; i--) {
    for (int j = 0; j < glowCount; j++) {
      digitalWrite(ledPins[i + j], HIGH);
    }
    delay(delayTime);
    for (int j = 0; j < glowCount; j++) {
      digitalWrite(ledPins[i + j], LOW);
    }
  }
}