int ledPins[] = {2, 3, 4, 5, 6};  

void setup() {
  for (int i = 0; i < 5; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  // Forward direction
  for (int i = 0; i < 5; i++) {
    digitalWrite(ledPins[i], HIGH);  
    delay(100);                      
    digitalWrite(ledPins[i], LOW);   
    delay(50);                       
  }

  // Reverse direction
  for (int i = 3; i >= 0; i--) {
    digitalWrite(ledPins[i], HIGH);
    delay(100);
    digitalWrite(ledPins[i], LOW);
    delay(50);
  }
}