window.addEventListener('scroll', () =>
{
  // Add class to body when scrolled.
  document.body.classList.toggle('is-scrolled', window.scrollY > 0);

  // Parallax effect.
  /**
   * @type {HTMLVideoElement}
   */
  const heroVid = document.querySelector('.hero video');
  heroVid.style.top = `${window.scrollY / 3}px`;

  // Highlight menu item when scrolled to section.
  let current = '';
  document.querySelectorAll('.section').forEach(section =>
  {
    const sectionTop = section.offsetTop;

    if (window.scrollY >= sectionTop - 70)
    {
      current = section.getAttribute('id');
    }
  });

  document.querySelectorAll('.nav-link').forEach(link =>
  {
    link.classList.remove('active');

    if (link.getAttribute('href') === `#${current}`)
    {
      link.classList.add('active');
    }
  });
});