const int mq2Pin = A0;
const int ledRed = 2;
const int ledGreen = 7;

const int threshold = 400;

void setup() {
  pinMode(ledRed, OUTPUT);
  pinMode(ledGreen, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(mq2Pin);

  Serial.print("Sensor Value: ");
  Serial.println(sensorValue);

  if (sensorValue > threshold) {
    digitalWrite(ledRed, HIGH);
    digitalWrite(ledGreen, LOW);
    delay(100);
    digitalWrite(ledRed, LOW); // turn off green led for flash
  } else {
    digitalWrite(ledRed, LOW);
    digitalWrite(ledGreen, HIGH);
    delay(100);
    digitalWrite(ledGreen, LOW); // turn off green led for flash
  }
  delay(1000);
}