#define echoPin 2 
#define trigPin 3 
#define buzzerPin 13

long duration; 
int distance; 

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

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

  digitalWrite(trigPin, HIGH); 
  delayMicroseconds(10); 

  digitalWrite(trigPin,LOW); 
          
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.0344 / 2;
  
  if (distance > 100) {
    digitalWrite(buzzerPin, LOW);
  }
  
  if (distance < 100 && distance > 30) {
    digitalWrite(buzzerPin, HIGH);
    delay(4000);
    digitalWrite(buzzerPin, LOW);
    delay(1000);
  }

  if (distance < 20 && distance > 10) {
    digitalWrite(buzzerPin, HIGH);
    delay(2000);
    digitalWrite(buzzerPin, LOW);
    delay(1000);
  }
  
  if (distance < 10 && distance > 1) {
    digitalWrite(buzzerPin, HIGH);
    delay(1000);
    digitalWrite(buzzerPin, LOW);
    delay(1000);
  }

  if (distance < 1) {
    digitalWrite(buzzerPin, HIGH);
    delay(500);
    digitalWrite(buzzerPin, LOW);
    delay(500);
  }
  
  delay(100);
  
}