#define LED 13
#define BTN 12

class ClickButton {
  private:
    bool state = HIGH;
    uint8_t btnPin;
    bool lastBtnState;
    bool currBtnState;

  public:
    ClickButton(uint8_t pin) {
      btnPin = pin;
    }
    
    void init() {
      pinMode(btnPin, INPUT_PULLUP);
      currBtnState = digitalRead(btnPin);
    }
    
    bool isPressed() {
      lastBtnState = currBtnState;
      currBtnState = digitalRead(btnPin);
      delay(5);
      return lastBtnState == HIGH && currBtnState == LOW;
    }
};

ClickButton btn = ClickButton(BTN);

void setup() {
  pinMode(LED, OUTPUT);
  btn.init();
}

bool state = LOW;

void loop() {
  if(btn.isPressed())
    state = !state;

  digitalWrite(LED, state);
}