// defines pins numbers
const int trigPin = 2;
const int echoPin = 3;
const int buzzer = 4;
const int ledPin = 5;

// defines variables
long duration;
int distance;
int safetyDistance;

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT);  // Sets the echoPin as an Input
  pinMode(buzzer, OUTPUT);  // Buzzer pin
  pinMode(ledPin, OUTPUT);  // LED pin
  Serial.begin(9600);       // Starts the serial communication
}

void loop() {
  // Clears the trigPin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  // Sets the trigPin on HIGH state for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);

  // Calculating the distance
  distance = duration * 0.0343 / 2; // Conversion to cm

  // Safety distance check
  safetyDistance = distance;
  if (safetyDistance <= 200) {
    tone(buzzer, 1000);            // Generate a 1 kHz tone
    digitalWrite(ledPin, HIGH);    // Turn on LED
  } else {
    noTone(buzzer);                // Stop the tone
    digitalWrite(ledPin, LOW);     // Turn off LED
  }

  // Prints the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.println(distance);

  // Short delay to stabilize the loop
  delay(200);
}