int red = 13;
#define ECHO_PIN 2
#define TRIG_PIN 3
#define buzzer 12

bool buzzerFlag = false;

void setup() {
  Serial.begin(9600);
  pinMode(red, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(buzzer, OUTPUT);
}

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

  int duration = pulseIn(ECHO_PIN, HIGH);
  float distance = duration * 0.034 / 2;

  Serial.print("Duration: ");
  Serial.print(duration);
  Serial.print(" - Distance: ");
  Serial.println(distance);

  if (distance <= 50) {
    digitalWrite(red, HIGH);
    if(!buzzerFlag){
      tone(buzzer, 2000, 500);
      buzzerFlag = true;
    }
  } else {
    digitalWrite(red, LOW);
    buzzerFlag = false;
  }

  delay(1500);
}