#include <avr/io.h>
#include <util/delay.h>

#include <stdbool.h>

#define LED_PORT PORTB0
#define BTN_PORT PIND2

int main(void) {
  // set pin to output
  DDRB |= (_BV(LED_PORT));

  while (true) {
    bool cur = (PIND & _BV(BTN_PORT));
    if (!cur)
      PORTB |= (_BV(LED_PORT));
    else
      PORTB &= ~(_BV(LED_PORT));
    _delay_ms(20.f);
  }
}