int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);

  Serial.println("System Started");     // ✅ print once
  Serial.println("Type 1 to ON LED");  
  Serial.println("Type 0 to OFF LED"); 
}

void loop() {
  if (Serial.available()) {
    String data = Serial.readString();
    data.trim();

    Serial.print("Received: ");   // ✅ print input
    Serial.println(data);

    if (data == "1") {
      digitalWrite(ledPin, HIGH);
      Serial.println("LED ON");
    }
    else if (data == "0") {
      digitalWrite(ledPin, LOW);
      Serial.println("LED OFF");
    }
  }
}