const int trigPin = 7;
const int echoPin = 6;

const int ledPin1 = 8;
const int ledPin2 = 9;
const int ledPin3 = 10;
const int ledPin4 = 11;

void setup() {
  // put your setup code here, to run once:
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  pinMode(ledPin4, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  //Measure distance
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.0343 / 2; //Convert duration to distance in cm
  Serial.println(distance);

  //Turn off all LEDs
  digitalWrite(ledPin1, LOW);
  digitalWrite(ledPin2, LOW);
  digitalWrite(ledPin3, LOW);
  digitalWrite(ledPin4, LOW);

  //Light up the LED based on distance ranges
  if (distance < 100 && distance >= 0)
  {
    digitalWrite(ledPin1, HIGH);
  }
  else if (distance > 100 && distance < 200)
  {
    digitalWrite(ledPin2, HIGH);
  }
  else if (distance > 200 && distance < 300)
  {
    digitalWrite(ledPin3, HIGH);
  }
  else if (distance > 300 && distance < 400)
  {
    digitalWrite(ledPin4, HIGH);
  }
}