CSS custom properties pierce through shadow DOM. That being said, there is the on-going ::part and ::theme proposal that would allow components to safely expose some of their internals outside their shadow tree to be customized. Well, speed is one reason. LWC specifically restricts the parent from messing with the child component's presentation via the use of Shadow DOM. Important¶. If you want to set some non-inheritable property (like padding - see full list here). Shadow boundary: the place where the shadow DOM ends, and the regular DOM begins. So I guess the only way to do this for non-inheritable properties is by either injecting CSS via the template (e.g. About a year ago, Twitter announced it would start displaying embedded tweets with the shadow DOM rather than an
