int timer = 35; // Delay time between steps

void setup() {
  // Set pins 2-10 as outputs by writing to DDRD and DDRB memory addresses
  *((volatile uint8_t *)0x2A) |= 0b11111100; // DDRD: Set pins 2-7 as outputs
  *((volatile uint8_t *)0x24) |= 0b00000011; // DDRB: Set pins 8-9 as outputs
}

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 memory addresses
void setPin(int pin, bool state) {
  if (pin >= 2 && pin <= 7) {
    // PORTD (pins 2-7) at address 0x2B
    volatile uint8_t *portD = (volatile uint8_t *)0x2B;
    if (state) *portD |= (1 << pin);
    else *portD &= ~(1 << pin);
  } else if (pin >= 8 && pin <= 9) {
    // PORTB (pins 8-9) at address 0x25
    volatile uint8_t *portB = (volatile uint8_t *)0x25;
    if (state) *portB |= (1 << (pin - 8));
    else *portB &= ~(1 << (pin - 8));
  }
}