// Define pins
const int TRIG_PIN = 7;
const int ECHO_PIN = 6;
const int LED1_PIN = 3; // Close range
const int LED2_PIN = 4; // Medium range
const int LED3_PIN = 5; // Far range

float duration_us, distance_cm;

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(LED1_PIN, OUTPUT);
  pinMode(LED2_PIN, OUTPUT);
  pinMode(LED3_PIN, OUTPUT);
}

void loop() {
  // Trigger the ultrasonic sensor
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read the echo pulse
  duration_us = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance (cm)
  distance_cm = 0.0343 * duration_us / 2;

  // Turn on LEDs based on distance
  if (distance_cm < 50) {
    digitalWrite(LED1_PIN, HIGH);  // Very close
    digitalWrite(LED2_PIN, LOW);
    digitalWrite(LED3_PIN, LOW);
  } else if (distance_cm >= 50 && distance_cm < 100) {
    digitalWrite(LED1_PIN, LOW);
    digitalWrite(LED2_PIN, HIGH);  // Medium
    digitalWrite(LED3_PIN, LOW);
  } else {
    digitalWrite(LED1_PIN, LOW);
    digitalWrite(LED2_PIN, LOW);
    digitalWrite(LED3_PIN, HIGH);  // Far
  }

  delay(300); // Small delay for stability
}