volatile int ledState = LOW;

void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  pinMode(13, OUTPUT);
  Serial.println("Setup complete. Waiting for button press...");
  attachInterrupt(digitalPinToInterrupt(2), toggleLED, FALLING);
}

void loop() {
  digitalWrite(13, ledState);
}

void toggleLED() {
  Serial.println("HERE") ;
  ledState = !ledState;
}