text: #define F_CPU (1000000L)
  #include <avr/io.h>
  #include <util/delay.h>
  
  int main(void){
    DDRD |= _BV(PD7);
    DDRD &= ~( _BV(PD3) );
  
    while(1){
      if(PIND & _BV(PD3) ){
        PORTD ^= _BV(PD7);
        _delay_ms(100);
      }else{
        PORTD &= ~(_BV(PD7) );
      }
    }
  
    return 0;
  }
  