Fixed parallax effect and active menu item.

public/assets/js/header.js

@@ -1,4 +1,34 @@
 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');
+    }
+  });
 });