#define echo_pin 16
#define trig_pin 17
#define ledred 12
#define ledyellow 14
#define ledgreen 27

void setup() {
  Serial.begin(115200);
  pinMode(trig_pin, OUTPUT);
  pinMode(echo_pin, INPUT);
  pinMode(ledred, OUTPUT);
  pinMode(ledyellow, OUTPUT);
  pinMode(ledgreen, OUTPUT);
}

void loop() {
  digitalWrite(trig_pin, LOW);
  delayMicroseconds(2);
  digitalWrite(trig_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig_pin, LOW);
  int duration = pulseIn(echo_pin, HIGH);
  float distance = duration * 0.034 / 2;

  if (distance > 200){
    digitalWrite(ledgreen, HIGH);
    digitalWrite(ledred, LOW);
    digitalWrite(ledyellow, LOW);
  }
  else if (distance < 200 && distance > 100) {
    digitalWrite(ledyellow, HIGH);
    digitalWrite(ledred, LOW);
    digitalWrite(ledgreen, LOW);
  }
  else if (distance < 100) {
    digitalWrite(ledred, HIGH);
    digitalWrite(ledgreen, LOW);
  }
  else {}
}