int led[10] ={3,4,5,6,7,9,10,11,12,13};
int posisi = 1;
bool maju = true;

void setup() {

  for(int a =0; a<10; a++)
  {
   pinMode(led[a], OUTPUT);
  }  

  pinMode(2, INPUT);
}

void loop() {
  
  for(int b=0; b<10; b++){
  
  if(b == (posisi-1) ) digitalWrite(led[b], HIGH);
  else digitalWrite(led[b], LOW);
  
  if(digitalRead(2) == LOW) break;

  }

  if( posisi == 10 ) maju = false;
  if( posisi == 1 ) maju = true;

  if(maju) posisi++;
  else posisi--;
  
  delay(100);

}