#define led 4  
#define bouton 2

void setup() {
  DDRD |= (1 << led);

  DDRD &= !(1 << bouton);
  PORTD |= (1 << bouton); // Activation Pull_Up
}

void loop() {

  if (!(PIND & (1 << bouton))) { 
    delay(100);
     while (!(PIND & (1 << bouton))) {
    }
    PORTD ^= (1 << led);
  }
}