One Technique that I found intresting is that every page has a different color. Like HTML uses red for it page, and CSS uses a blue color for it page. When you click HTML, and go to it page it highlight HTML on the left side of the page. The thing they uses is a var color to correspond to sticky-header-container, so they can match up to each other. Another thing that cought my eye was that the li class section they use was a flex.