#define Trigpin 7
#define Echopin 8
#define ledPin 9

void setup() {
  pinMode(Trigpin, OUTPUT);
  pinMode(Echopin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  long duration, distance;

  digitalWrite(Trigpin, LOW);
  delayMicroseconds(2);
  digitalWrite(Trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(Trigpin, LOW);

  duration = pulseIn(Echopin, HIGH);
  distance = (duration / 2) / 29.1; 

  int maxDistance = 100; // Maximum distance in cm  full brightness

  
  int brightness = map(distance, 0, maxDistance, 0, 255); 
  brightness = constrain(brightness, 0, 255); 

 
  analogWrite(ledPin, brightness);

  
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  delay(500);
}