const int switchL = 2;
const int switchR = 3;
const int firstPin = 8;
const int lastPin = 13;

int currentPin = firstPin;
int direction = 1;       // 1 = hacia la derecha, -1 = hacia la izquierda
unsigned long lastUpdate = 0;
const unsigned long stepDelay = 500;
bool ledOn = false;

void setup() {
  for (int i = firstPin; i <= lastPin; i++) pinMode(i, OUTPUT);
  pinMode(switchL, INPUT_PULLUP);
  pinMode(switchR, INPUT_PULLUP);
}

void loop() {
  // lee la dirección deseada en CADA vuelta del loop, sin bloquear
  if (digitalRead(switchL) == 1) direction = -1;
  else if (digitalRead(switchR) == 1) direction = 1;

  unsigned long now = millis();
  if (now - lastUpdate >= stepDelay) {
    lastUpdate = now;
    if (ledOn) {
      digitalWrite(currentPin, LOW);
      ledOn = false;
      currentPin += direction;
      if (currentPin > lastPin) currentPin = firstPin;
      if (currentPin < firstPin) currentPin = lastPin;
    } else {
      digitalWrite(currentPin, HIGH);
      ledOn = true;
    }
  }
}