Oh, EC: I don't know whether to thank you or hate you for posting this!
I'd played it a while ago (or more accurately, an earlier version called "1024" - essentially the same game, but the tiles start at "1" and the target's 1024), and it is indeed horribly addictive.
I looked it up and apparently the game dates from 2014 - a bit earlier than I thought.
Unfortunately; as with other FMs I can't resist, so instead of continually accessing the site I've downloaded a Windows app version.
Still not reached the 2048 tile yet, but current highest score? 15,996...