int arrayLed [] = {0,1,2,3,4,5,6,7};

void setup() {
  for(int i = 0; i < 8; i++){
    pinMode(arrayLed[i], OUTPUT); // i++ = i plus 1
  }

}

void loop() {
  //int i = 0;
  //digitalWrite(arrayLed[i], HIGH);
  //i +=1;
  for(int i = 0; i < 8; i++){
    digitalWrite(arrayLed[i], HIGH); // i++ = i plus 1
    delay(500);
  }
  
    for(int i = 7; i > -1; i--){
    digitalWrite(arrayLed[i], LOW); // i++ = i plus 1
    delay(500);
  }
}