main.c

#include <avr/io.h>
#include <avr/sleep.h>

void main()
{
  static char state __attribute__ ((section (".noinit")));

  DDRB |= (1 << PB2);
  if (state)
  {
    PORTB |= (1 << PB2);
  }
  else
  {
    PORTB &= ~(1 << PB2);
  }
  state = !state;
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  sleep_cpu();
}