LED Candle Effect Question

Projects Programming
17 
void candlesEffect() {

  const short FLAME_PWM_RANGE = 2 * LED_MAX_PWM / 3;
  const short FLAME_SPEED = 400;
  const byte pins[] = {LEDS_LEFT_PIN, LEDS_RIGHT_PIN};

  static short targetPwm[sizeof(pins)];
  static short currentPwm[sizeof(pins)];
  static unsigned long prevMicros[sizeof(pins)];

  for (int i = 0; i < sizeof(pins); i++) {
    if (micros() - prevMicros[i] > FLAME_SPEED) {
      prevMicros[i] = micros();
      if (currentPwm[i] == targetPwm[i]) {
        targetPwm[i] = random(LED_MAX_PWM - FLAME_PWM_RANGE, LED_MAX_PWM);
      }
      currentPwm[i] += targetPwm[i] < currentPwm[i] ? -1 : 1;
      analogWrite(pins[i], currentPwm[i]);
    }
  }
}

from SunriseClock/SunriseClock.ino at main · JAndrassy/SunriseClock · GitHub