I looked at this and thought "What am I looking at? There's some janky animation as things shift around but what's the bit I'm missing??" and then it slowly dawned on me clicking around a bit more that it must be the poxy animation bit itself.
I mean I guess web consumers are just SCREAMING OUT for this and I've been living under a rock?
Obviously I am old and grumpy but holy crap this is exciting browser development now. Seesh.