const int trigPin = 4;
const int echoPin = 3;
const int piezoPin = 6;
const int ledPin = 7;

int distance;
int duration;

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(piezoPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
}

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

  duration = pulseIn(echoPin, HIGH,10000); // added a timeout of 10000 to avoid 0 value
  distance = duration * 0.034 / 2;

  if (distance != 0){ // added a check if the distance is not 0
    Serial.print("Distance: ");
    Serial.println(distance);
  }

  if (distance < 30 && distance != 0) {
    digitalWrite(ledPin, HIGH);
    playToccata();
    Serial.println("Playing Toccata and Fugue in D Minor");
  } else {
    noTone(piezoPin);
    digitalWrite(ledPin, LOW);
  }
  delay(100);
}

void playToccata() {
  int note[] = {
    659, 622, 659, 622, 659, 494, 587, 523, 622, 659, 622, 659, 622, 494, 587, 392,
    330, 294, 262, 330, 392, 440, 494, 523, 587, 659, 622, 659, 622, 659, 494, 587, 523, 622, 659, 622, 659
  };

  int tempo[] = {
    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12
  };

  for (int i = 0; i < sizeof(note)/sizeof(note[0]); i++) {
    int duration = tempo[i] * 30;
    tone(piezoPin, note[i], duration);
    delay(duration);
    if (i == sizeof(note)/sizeof(note[0]) - 1) {
      noTone(piezoPin);
    }
  }
}