[leonkenneth]

I am not a maintainer and I just tried it briefly so I am not 100% sure of the allegations they make on their front-page, but it seems like http://gridstylesheets.org are using Workers to run their layout algorithm (Cassowary Constraint Solver) and absolute-position elements (using 3D transforms).

EDIT: Searching for "Worker" right now didn't bring any mention, but it seems it is a very recent edit (cf https://github.com/gss/gss.github.io/commit/d6a931e3629d4b5d...).