// Define the pins used for the ultrasonic sensor
const int trigPin = 4;
const int echoPin = 5;

// Define the pins used for the LEDs
const int redPin = 12;
const int greenPin = 13;
const int yellowPin = 14;

void setup() {
  // Initialize the serial communication
  Serial.begin(9600);

  // Initialize the ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Initialize the LED pins
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
}

void loop() {
  // Trigger the ultrasonic sensor by sending a 10 microsecond pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the pulse from the ultrasonic sensor
  long duration = pulseIn(echoPin, HIGH);

  // Convert the duration to distance in centimeters
  int distance = duration * 0.034 / 2;

  // Print the distance to the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Blink the LED colors based on the distance
  if (distance < 10) {
    digitalWrite(redPin, HIGH);
    delay(100);
    digitalWrite(redPin, LOW);
    delay(100);
    
    digitalWrite(greenPin, LOW);
    digitalWrite(yellowPin, LOW);
  } else if (distance < 20) {
    digitalWrite(redPin, LOW);
    
    digitalWrite(greenPin, LOW);
    digitalWrite(yellowPin, LOW);
    
    digitalWrite(yellowPin, HIGH);
    delay(250);
    digitalWrite(yellowPin, LOW);
    delay(250);
  } else {
    digitalWrite(redPin, LOW);
    
    digitalWrite(yellowPin, LOW);
    digitalWrite(greenPin, HIGH);
  }
}