#define BUTTON_PIN 2
#define LED_PIN 13

void setup() {
  DDRD &= ~(1 << DDD2); // set digital pin 2 as input
  DDRB |= (1 << DDB5); // set digital pin 13 as output
}

void loop() {
  if (PIND & (1 << PIND2)) {
    // if button is pressed, turn on LED
    PORTB |= (1 << PORTB5);
  } else {
    // if button is not pressed, turn off LED
    PORTB &= ~(1 << PORTB5);
  }
}