It's a social game, basically think-of-a-word-starting-with-one-of-these-three-letters-that-fits-one-of-these-three-categories. Players get to decide whether the suggested word does indeed fit, which is where the social element comes in.
I noticed this at Christmas and thought it might be something I could get for my students to play, but I wandered around the shop looking at books for too long and it had sold out. I didn't realise it was by Doruk at the time.
It turns out that my experience probably wasn't unique. 300,000 copies were sold over Christmas. Cheerful packaging matching a quirky name that fits the gameplay — it's a good combination.
There are plenty of commercial MMOs with fewer than 300,000 players. I'm in the wrong business!