#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));

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