Set the theme attribute

Themes switch through the data-theme attribute. Put it on <html>, or on any element to theme only that subtree.

<html data-theme="light">

Supported values: light and dark. Without the attribute the light values apply. The variables are declared per attribute value, so a nested element with its own data-theme overrides its ancestors. The live examples in these docs do exactly that: each example frame carries its own data-theme and the site's own colour mode is unaffected.

A second reference theme is planned.