int timer = 35; // Delay time between steps

void setup() {
  // Set pins 2 to 10 as outputs
  DDRD |= 0b11111100; // Pins 2-7 (PORTD)
  DDRB |= 0b00000011; // Pins 8-9 (PORTB)
}

void loop() {
  // Move LEDs forward (pins 2-10)
  for (int thisPin = 2; thisPin <= 10; thisPin++) {
    setPin(thisPin, HIGH);
    delay(timer);
    setPin(thisPin, LOW);
  }

  // Move LEDs backward (pins 10-2)
  for (int thisPin = 10; thisPin >= 2; thisPin--) {
    setPin(thisPin, HIGH);
    delay(timer);
    setPin(thisPin, LOW);
  }
}

// Function to set pin HIGH or LOW using direct port manipulation
void setPin(int pin, bool state) {
  if (pin >= 2 && pin <= 7) {
    // PORTD (pins 2-7)
    if (state) PORTD |= (1 << pin);
    else PORTD &= ~(1 << pin);
  } else if (pin >= 8 && pin <= 9) {
    // PORTB (pins 8-9)
    if (state) PORTB |= (1 << (pin - 8));
    else PORTB &= ~(1 << (pin - 8));
  }
}