Looks great, and generally very smooth for me.<p>When the tooltip changes location it is quite jarring, but I have no good solution for that :) - perhaps only flip the position when you would otherwise obscure the underlying visualisation, rather than when you cross the centre? You could then have the tooltip 'push up' to the edge when you navigate close to it, but when the tooltip would otherwise not be obscuring. There was a submission to HN not too long ago that featured a library that would simplify creating this kind of behaviour, but alas I cannot find it.<p>It took me a while to click on the different years at the bottom, and until I did I wasn't certain what the tooltip data was representing. Probably not a problem, as the discovery was fun, but I guess many might not explore that far.<p>Out of interest, what were your design thought process when choosing a map projection?