// Include required libraries
#include <Arduino.h>

// Define the pins for the LEDs
const int ledPins[] = {19, 18, 5, 17}; // Change pins as per your setup

// Define the pin for the push button
const int buttonPin = 0; // Change pin as per your setup

// Variable to store the current count
int count = 3; // Start from the last LED

// Variable to store the state of the LED counter
bool ledCounterOn = false;

void setup() {
  // Set all LED pins as output
  for (int i = 0; i < 4; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
  
  // Set the push button pin as input with internal pull-up resistor
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  // Read the state of the push button
  int buttonState = digitalRead(buttonPin);
  
  // Toggle LED counter on/off when the button is pressed
  if (buttonState == LOW) {
    ledCounterOn = !ledCounterOn;
    delay(50); // Debouncing delay
  }
  
  // If LED counter is on, decrement count and update LEDs
  if (ledCounterOn) {
    count--;
    updateLEDs();
    delay(500); // Delay between each LED
  }
}

void updateLEDs() {
  // Reset count to 3 if it reaches -1
  if (count == -1) {
    count = 3;
  }
  
  // Turn off all LEDs
  for (int i = 0; i < 4; i++) {
    digitalWrite(ledPins[i], LOW);
  }
  
  // Turn on the current LED
  digitalWrite(ledPins[count], HIGH);
}