Echo JS 0.11.0

At this point, you might as well use JSS or similar.

Not exactly, this is using CSS Variables to theme with a JS object interface for users to easily interface with CSS-in-JS solutions and programmatic JS in general. Theming and styling with something like JSS has a different bundle size, performance, implementation, and API surface area implications. This is to encourage more use of "back to web standards" and plain old CSS.