document.addEventListener('DOMContentLoaded', function () {
  const header = document.getElementById('main-header');
  const logo = document.getElementById('logo-img');
  const scrollThreshold = 100; // 滚动多少像素后开始缩小

  window.addEventListener('scroll', function () {
    if (window.scrollY > scrollThreshold) {
      header.classList.add('small-header');
    } else {
      header.classList.remove('small-header');
    }
  });
});