int buttonPin = PA0;
int ledPin = PC13;

volatile bool ledState = false;

volatile unsigned long lastInterruptTime = 0;

void handleInterrupt() {

  unsigned long currentTime = millis();

  // Debounce check
  if (currentTime - lastInterruptTime > 200) {

    ledState = !ledState;

    digitalWrite(ledPin,
                 ledState ? LOW : HIGH);

    lastInterruptTime = currentTime;
  }
}

void setup() {

  pinMode(buttonPin, INPUT_PULLUP);

  pinMode(ledPin, OUTPUT);

  digitalWrite(ledPin, HIGH);

  attachInterrupt(
    digitalPinToInterrupt(buttonPin),
    handleInterrupt,
    FALLING
  );
}

void loop() {

}