// Pin numbers for the LEDs
const int ledPins[] = {2, 3, 4}; // Define an array to hold the pin numbers of the LEDs
const int numLeds = sizeof(ledPins) / sizeof(ledPins[0]); // Calculate the number of LEDs connected
const int delayTime = 200; // Adjust the delay time for the desired speed

void setup() 
{
  // Initialize each LED pin as an output
  for (int i = 0; i < numLeds; i++) 
  {
    pinMode(ledPins[i], OUTPUT); // Set each pin in the ledPins array as an OUTPUT pin
  }
}

void loop() {
  // Turn on LEDs from left to right
  for (int i = 0; i < numLeds; i++) 
  {
    digitalWrite(ledPins[i], HIGH); // Turn on the LED at the current index position
    delay(delayTime); // Wait for delayTime milliseconds before proceeding to the next LED
    digitalWrite(ledPins[i], LOW); // Turn off the LED at the current index position
  }
  
  // Turn off LEDs from right to left
  for (int i = numLeds - 2; i >= 1; i--) 
  {
    digitalWrite(ledPins[i], HIGH); // Turn on the LED at the current index position
    delay(delayTime); // Wait for delayTime milliseconds before proceeding to the next LED
    digitalWrite(ledPins[i], LOW); // Turn off the LED at the current index position
  }
}