This is a blast. I stumbled on it today, and found myself losing a couple of hours messing around with it.
It just goes to show, it's the really simple ideas that can go ballistic and make a huge impact. Doing a little snooping around, there are thousands of websites devoted to this little game. I'm not even aware yet how long it's been doing the round on the internet, but given how quickly things can take off on the net, I wouldn't be surprised if it's only been around for a few weeks.