#define LED_PIN 2
#define BUTTON_PIN 4

volatile bool ledEnabled = true; // 'volatile' is required for variables used in interrupts
unsigned long lastInterruptTime = 0;

// The "Interrupt Service Routine" (ISR) - Must be fast!
void IRAM_ATTR handleButton() {
  unsigned long interruptTime = millis();
  // Simple software debounce: ignore interrupts within 200ms
  if (interruptTime - lastInterruptTime > 200) {
    ledEnabled = !ledEnabled;
  }
  lastInterruptTime = interruptTime;
}

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  
  // Attach the interrupt to Pin 4, looking for a FALLING edge (High to Low)
  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), handleButton, FALLING);
}

void loop() {
  static unsigned long prevMillis = 0;
  if (ledEnabled) {
    if (millis() - prevMillis >= 1000) {
      prevMillis = millis();
      digitalWrite(LED_PIN, !digitalRead(LED_PIN)); // Toggle LED
    }
  } else {
    digitalWrite(LED_PIN, LOW);
  }
}