//Defines Pin Numbers
const int trigPin = 2;
const int echoPin = 3;
const int redLED = 4;
const int greenLED = 7;
const int threshold = 42;
//Defines Variables
long duration;
int distance;


unsigned long countdownStart = 0;
const unsigned long countdownDur = 3000;


void setup() {
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
  
}

void loop() {

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  // Measure distance converted to inches
  distance = ((duration * 0.034 / 2) / 2.54);
  Serial.println(distance);

  if (distance < 42) {
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
    countdownStart = millis();
  } 
  else {
   // if (countdownStart == 0) {
  //    countdownStart = millis();
   // }

    if (millis() - countdownStart >= countdownDur) {
      digitalWrite(redLED, LOW);
      digitalWrite(greenLED, HIGH);
    }
  }
}