const int trigPin = 17; // Ultrasonic sensor trigger pin
const int echoPin = 16; // Ultrasonic sensor echo pin

const int redLedPin = 12;  // Red LED pin
const int greenLedPin = 13; // Green LED pin

long duration;
int distance;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(greenLedPin, OUTPUT);

  digitalWrite(redLedPin, LOW);
  digitalWrite(greenLedPin, LOW);

  Serial.begin(9600);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2; // Calculate distance in cm

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance <= 4) {
    digitalWrite(redLedPin, HIGH);
    digitalWrite(greenLedPin, LOW);
  } else {
    digitalWrite(redLedPin, LOW);
    digitalWrite(greenLedPin, HIGH);
  }

  delay(1000); // Delay 1 second before next update
}