const int ledPin    = 15; // LED + resistor to GPIO 15
const int buttonPin = 14; // button to GPIO 14

void setup() {
  Serial.begin(115200);
  pinMode(ledPin,    OUTPUT);
  // INPUT_PULLUP means button unpressed → HIGH; pressed → LOW
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  bool pressed = (digitalRead(buttonPin) == LOW);

  if (!pressed) {
    // button NOT pressed ⇒ blink
    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    delay(500);
  } 
  else {
    // button pressed ⇒ LED constantly on
    digitalWrite(ledPin, HIGH);
  }
}