// Define constants for ultrasonic sensor pins
const int trigPin = 7;
const int echoPin = 6;

// Define LED pin
const int ledPin = 9;

// Variables for ultrasonic sensor
long duration;
int distance;

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);

  // Define pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Measure distance using ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

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

  // Print distance to serial monitor (optional)
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Set LED brightness based on distance
  if (distance > 200) {
    analogWrite(ledPin, 128); // 50% brightness
  } else if (distance <= 199) {
    analogWrite(ledPin, 255); // 100% brightness
  } else {
    analogWrite(ledPin, 0); // Turn off LED (if needed for undefined cases)
  }

  // Delay for stability
  delay(100); // Adjust delay as needed
}