Close but not exactly, there is no esoteric HTC stuff for example.
element.selector {
prototype: ClassName url(in-module.js);
color: blue;
...
}
That above is significantly better than almost-dead-at-birth WebComponents:
let customElementRegistry = window.customElements;
customElementRegistry.define('my-custom-element', MyCustomElement);
One simple CSS property instead of 20+ additional entities
https://developer.mozilla.org/en-US/docs/Web/Web_ComponentsUsed quite a lot actually, on half of machines where Sciter is installed (~500..600 mln machines :)