int delayTime = 500;
int currentLed = 0;
int lastLed = 0;
int dir = 1;
long timeChanged = 0;
byte  ledPin[] = {13,12,11,10,9,8,7,6,5,4};
const int BUTTON = 2;

void setup() {
  for(int i = 0; i <10; i++) {
    pinMode(ledPin[i], OUTPUT);
  }
  pinMode(BUTTON, INPUT);
  Serial.begin(9600);
  timeChanged = millis();
}

void loop() {
  if ((millis() - timeChanged) > delayTime) {
    int boton = digitalRead(BUTTON);
    digitalWrite(ledPin[lastLed], LOW);
    digitalWrite(ledPin[currentLed], HIGH);
    lastLed = currentLed;
    currentLed = currentLed + dir;
    if(currentLed == 9) {
      dir = -1;
    }
    if (currentLed == 0) {
      dir = 1;
    }
    if(boton) dir = -1;
    timeChanged = millis();
  }
}