I've started porting XenForo JS animations to CSS. Of course with performance improvements. The progress is not yet very far, but at least I can show you something to be impressed by. Here is the first pre-alpha version of the upcoming add-on called CSS-only animations. After you install it you'll only notice that your login bar now opens and closes faster. It opens significantly faster on mobile devices, so try it on your phone for example. Expose mask is not done yet. Please don't use this add-on in production, there's not much control of it over the styles nor it's functions. Enjoy!