const int trigPin = 19;
const int echoPin = 21;

#define SOUND_SPEED 0.034
#define CM_TO_INCH 0.393701

long duration;
float distanceCm;
float distanceInch;



void setup() {

  Serial.begin(9600);
 
  pinMode(trigPin, OUTPUT); 
  pinMode(echoPin, INPUT); 
  pinMode(18, OUTPUT); // buzzer
  pinMode(2, OUTPUT); // RGB blue
  pinMode(4, OUTPUT); // RGB green
  pinMode(5, OUTPUT); // RGB red
  
}

void loop() {
  
  delay(2000);

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
 
  duration = pulseIn(echoPin, HIGH);
  
  distanceCm = duration * SOUND_SPEED/2;
  
  Serial.println(" Distance (cm): ");
  Serial.println(distanceCm);


  if(distanceCm <= 40){

    digitalWrite(2, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    delay(1000);
    digitalWrite(2, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    delay(1000);
    
  }

if(distanceCm >= 40 && distanceCm <= 60){

  tone(18, 1500, 500); 
    
  }

if(distanceCm >= 60 && distanceCm <= 80){

  tone(18, 1200, 600); 
    
  }

if(distanceCm >= 80 && distanceCm <= 100){

  tone(18, 1000, 1000); 
    
  }


  tone(18, 0, 0); 

 
  
}