Composable Styles

Compose abstract core components with concrete part identity. A core List owns the list class and a core item component owns item; a part adds its domain class, such as videos on the list and video on each item, without replacing the core structure or behavior. The resulting root may be class="list videos" and each item class="item video". Both classes describe meaning or structural role. Do not add visual variant classes such as card or threeDimensional to markup. Style the abstract role first, then use combined role-and-domain selectors only for differences needed by that part. Keep CSS appearance in site or theme stylesheets.