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

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP); // uses internal resistor
}

void loop() {
  if (digitalRead(buttonPin) == LOW) { // button pressed
    digitalWrite(ledPin, HIGH);
    delay(300);
    digitalWrite(ledPin, LOW);
    delay(300);
  } else {
    digitalWrite(ledPin, LOW);
  }
}