const int buttonPin = 2;
const int ledPin = 13;

int count = 0;

unsigned long lastPressTime = 0;
unsigned long lastValidPressTime = 0;
volatile boolean isPressed = false;

void buttonPressed() {
  isPressed = true;
}

void setup() {
  pinMode(buttonPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(buttonPin), buttonPressed, RISING);
  
  Serial.begin(9600);
}

void loop() {
  if (isPressed) {
    isPressed = false;

    const int now = millis();
    if ((now - lastPressTime) > 50) { // 50ms for bounce.
      lastPressTime = now;

      if ((now - lastValidPressTime) > 500) { // 500ms for press interval.
        lastValidPressTime = now;
        count += 1;
        Serial.println(count);
      }
    }
  }
}