int buzzerPin = 7;
int LEDblue = 12;
int LEDred = 8;
int trigPin = 10;
int echoPin = 9;

long duration, distance;

void setup() {
  // put your setup code here, to run once:
pinMode(LEDblue, OUTPUT);
pinMode(LEDred, OUTPUT);
pinMode(buzzerPin, OUTPUT);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
Serial.begin(9600);
}

void loop() {
  // turning on and off the transmitter
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);


//measuring the distance
duration = pulseIn(echoPin, HIGH);
distance = duration*0.034/2;

//displaying distance
Serial.print("distance: ");
Serial.println(distance);

if (distance>250) { //if the distance is greater than 250
  digitalWrite(LEDred, HIGH);
  digitalWrite(LEDblue, HIGH);
  tone(buzzerPin, 500);
}
else if (distance >=150) { //if the distance equal or greater 150 but less than 250 
  digitalWrite(LEDred, LOW);
  digitalWrite(LEDblue, HIGH);
  tone(buzzerPin, 1000);
}
else { //if the distance is less than 150
  digitalWrite(LEDred, LOW);
  digitalWrite(LEDblue, LOW);
  noTone(buzzerPin);
}
}