Knight Rider leds for particle

knight_rider.ino

int leds[] = {D4, D3, D2, D1, D0};
int led_count = 5;
int timer = 15;

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

void activateLed(int led, int direction) {
  for (int i = 0; i < led_count; i++) {
    if (i == led || i == led + direction) {
      digitalWrite(leds[i], HIGH);
      delay(timer);
    } else {
      digitalWrite(leds[i], LOW);
      delay(timer * 2);
    }
  }
}

void loop() {
  for (int i = 0; i < led_count; i++) {
    activateLed(i, -1);
  }
  for (int i = led_count -1; i >= 0; i--) {
    activateLed(i, 1);
  }
}