int gasPin = A0;        // MQ-2 connected to A0
int ledRedPin = 13;    // Red LED (gas detected)
int ledBluePin = 11;   // Blue LED (normal)
int buzzerPin = 12;    // Buzzer pin

void setup() {
  pinMode(ledRedPin, OUTPUT);
  pinMode(ledBluePin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int gasValue = analogRead(gasPin);
  Serial.println(gasValue);

  if (gasValue > 400) {        // Gas detected
    digitalWrite(ledRedPin, HIGH);
    digitalWrite(ledBluePin, LOW);
    digitalWrite(buzzerPin, HIGH);
  } else {                     // Normal
    digitalWrite(ledRedPin, LOW);
    digitalWrite(ledBluePin, HIGH);
    digitalWrite(buzzerPin, LOW);
  }

  delay(500);
}