A simple navigation that auto-hides when the user scrolls down, and becomes visible when the user scrolls up.
Auto-hiding navigations have been around for quite some time now, in particular on mobile devices. The idea behind this UX pattern is simple yet efficient: we want the navigation to be easy to reach all the time, so we stick it on top. However, we auto-hide it when the user scrolls down, to create more room for the content. If the user scrolls up, we interpret his behaviour as a will to access the navigation, so we bring it back.