2. As for the polyfill in the demo, if you click the “Resources” button on the bottom left, you’ll see that it shows this script as an external JavaScript resource. Some of the core controls are a little verbose and do rely on at least a moderate knowledge of how the DOM works. Nodes inside Shadow DOM by default have no special styles, so properties that inherit such as font-family or color will inherit their values from the Shadow DOM's ancestors. CSS Shadow Parts allow developers to style CSS properties on an element inside of a shadow tree. See the Pen Embedded third-party content is a pretty good use case. One of the core features of Shadow DOM is the shadow boundary. You set a height and that’s that. That means the ::part() selector is now supported in Chrome, Edge, Opera, Safari, and Firefox. This means that, unless the cascade results in a value, the value will be determined by inheritance. “capable of isolating CSS and JavaScript, almost like an