int buttonPin = 2;
bool prevState = false;
bool lightOn = false;
bool isLight = false;
float sec = 0.5;
long time = 0;


void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  bool buttonState = digitalRead(buttonPin);
  if (buttonState != prevState) {
    prevState = buttonState;
    if (buttonState){
      Serial.println("Кнопка нажата!");
      lightOn = !lightOn;
      (lightOn) ? Serial.println("Мигает!") : Serial.println("Не мигает!");;
    } else {
      Serial.println("Кнопка не нажата!");
      digitalWrite(13, false);
    }
  }
  if (lightOn) {
    if (millis()-time>sec*1000) {
      time=millis();
      turn();
    }
  }
}

void turn() {
  isLight=!isLight;
  digitalWrite(13, isLight);
}