Scroll the column. The video nearest the centre starts playing on its own and muted; the others hold a still frame. Only one plays at a time, and it pauses the moment it leaves. The only chrome on a playing tile is the running time, top-left, and the mute toggle, top-right: tap it and the choice sticks to every video after. Tap a tile to open the full player, where the controls fade away during playback and a finished clip advances to the next. Muted-by-default is not only a taste call: browsers block autoplay with sound, so muted is the only playback that can start by itself. That platform rule is the reason the timeline looks the way it does. Reduced-motion holds every frame still and lets you play by hand. After the X (Twitter) timeline.

Mechanism: IntersectionObserver picks the most-visible tile; one player at a time.