void setup() {
  DDRD = 0xFF;
}

void loop() {
  PORTD = 0;
  delay(200);
  for (int i = 0; i < 8; i++) {
    PORTD = PIND |= 1<<i;
    delay(100);
  }
  delay(50);
  for (int j = 7; j > -1; j--) {
    PORTD = PIND &= ~(1<<j);
    delay(100);
  }
}