CSS is amazing, but the HTML DOM isn't. It's just so heavy. Maybe if JSON or some similar format could replace HTML/XML, it could be made lighter? Better, I think, would be to use a human readable format like Eno. It's as terse but much easier to read than JSON.
CSS is arguably the best means of UI customization. Consider an example of graphic-editing of UI elements: https://initialaudio.com/how-to-skin-sektor/ Using CSS, all elements in that project could potentially be done without graphics. Pros practically all designers now know CSS it's vastly capable Cons can't really decouple CSS from HTML whereas HTML is the biggest performance bottleneck (we'll solve this using different means) The Problem Unfortunately, CSS can get incredibly bulky. So what if we could design using CSS in a way that could feasibly be compiled to a local app? In general, everything would be styled using CSS, in the same bulky way it exists in browsers. But when compiled, it's no longer bulky. Benefits we have the full flexibility of CSS for all apps we have the full speed of native apps if needed