const boxes = document.querySelectorAll('.box');
    let index = 0;

    function highlightNext() {
      boxes.forEach((box, i) => {
        box.classList.toggle('highlight', i === index);
      });
      index = (index + 1) % boxes.length;
    }

    highlightNext(); // 초기 강조
    setInterval(highlightNext, 3000); // 3초마다