This is a term for an element query that wraps a block of CSS rules that apply to different elements other than the scoped element itself. The syntax I am proposing is a container-style element query syntax.
@element '#sidebar' and (max-width: 300px) {
#sidebar .widget {
font-size: 10pt;
}
}A non container-style element query syntax would allow you to write responsive conditions for one element, and only change styles for that one element depending on its own condition.