const int buttonPin = D1;
const int ledPin = D0;
const int DEBOUNCE_TIME = 100;
bool buttonPressed = 0;
int debounceCount = 0;

void setup() {

  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
}

void loop() {
  
  bool buttonState = digitalRead(buttonPin);
  bool ledState = digitalRead(ledPin);

  if (buttonState && debounceCount < DEBOUNCE_TIME) debounceCount++;

  if (!buttonState) debounceCount--;

  if (debounceCount >= DEBOUNCE_TIME && !buttonPressed){ // button is officially pressed
    digitalWrite(ledPin, abs(ledState - 1));
    buttonPressed = true;
  } else if (!buttonState && debounceCount < 0) { // button is officially not pressed
    debounceCount = 0;
    buttonPressed = false;
  }
}