But there is a replacement: TVML, TVJS, and TVML styles.

TVJS is basically JS and TVML styles is pretty much CSS. However, TVML is something else. It’s a markup language. It looks like HTML. But it’s not.

Start here: https://developer.apple.com/library/prerelease/tvos/documentation/LanguagesUtilities/Conceptual/ATV_Template_Guide/