const int trigPin = 8;
const int echoPin = 7;
const int buzzerPin = 9;

const int greenLED = 12;
const int yellowLED = 11;
const int redLED = 10;

$0
long duration;
float distance;

void setup() {
  Serial.begin(115200);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);

  pinMode(greenLED, OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(redLED, OUTPUT);

  digitalWrite(trigPin, LOW);
}

void loop() {
  // --- Measure distance ---
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH, 30000); // 30 ms timeout

  if (duration == 0) {
    distance = -1;
    Serial.println("No echo detected");
  } else {
    distance = duration * 0.034 / 2; // cm
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");
  }

  // --- LED and buzzer logic ---
  digitalWrite(greenLED, LOW);
  digitalWrite(yellowLED, LOW);
  digitalWrite(redLED, LOW);

  if (distance == -1) {
    digitalWrite(redLED, HIGH); // Red: no object
    tone(buzzerPin, 1500);      // Panic beep
    Serial.println("Warning: No object detected!🤔");
  }
  else if (distance < 10) {
    digitalWrite(yellowLED, HIGH); // Yellow: too close
    tone(buzzerPin, 400);          // Alert beep
    Serial.println("Alert: Object very close!😱");
  }
  else if (distance > 50) {
    digitalWrite(redLED, HIGH);    // Red: too far
    tone(buzzerPin, 1000);         // Panic beep
    Serial.println("Warning: Object too far!😕");
  }
  else {
    digitalWrite(greenLED, HIGH); // Green: safe range
    noTone(buzzerPin);
    Serial.println("Object within safe range.😃");
  }

  delay(500);
}