void setup() {
  // put your setup code here, to run once:
  pinMode(9, OUTPUT); // red LED 10 sec
  pinMode(7, OUTPUT); // green LED 7 sec
  pinMode(8, OUTPUT); // yellow LED 9 sec

  Serial.begin(9600);  // serial monitor, essential to detect distance and reveal value
}

void loop() {
  // put your main code here, to run repeatedly:
  
  for (int green = 5; green >= 0; green--) {
    digitalWrite(9, LOW);
    digitalWrite(7, HIGH);
    digitalWrite(8, LOW);
    Serial.print("Green time left: ");
    Serial.print(green);
    Serial.println(" seconds");
    delay(1000);
  }

  for (int yellow = 5; yellow >= 0; yellow--) {
    digitalWrite(9, LOW);
    digitalWrite(7, LOW);
    digitalWrite(8, HIGH);
    Serial.print("Yellow time left: ");
    Serial.print(yellow);
    Serial.println(" seconds");
    delay(1000);
  }

  for (int red = 5; red >= 0; red--) {
    digitalWrite(9, HIGH);
    digitalWrite(7, LOW);
    digitalWrite(8, LOW);
    Serial.print("Red time left: ");
    Serial.print(red);
    Serial.println(" seconds");
    delay(1000);
  }
}