Noticed some interesting effects on YouTube's buttons today. Turns out they seem to be created by a <yt-light-shape> custom element.

Seems to be mostly CSS, it kind of works when I copy it into a separate file, but not quite (the effect shows, but it doesn't look as good). Something's still missing, and I wonder what exactly. Perhaps the outer elements provide additional styles or settings or variables — the text color looked off, too…