Number Game

I was flying and the flight magazine has an introduction from one of its editors saying that she is happy to introduce this game in the magazine. She is overwhelmed by the positive response from its passengers for the introduction of the game.

Then on my return journey, I was a bit surprised to see many people solving the game at the magazine. The guy on my next seat was having seperate papers of the game and was solving the whole time like for 3 hours. Any guess on the game?

Soduko! I guess this game has been a bit more than hyped up lately. Is this a great game? It is quite an interesting game and guess, keeps people's mind busy. But I haven't tried solving one yet. Is this an American game? Is it something new? Because I have started a mention on this game in many places recently.

My questions on this are
- Does it have only one solution?
- Why people say it takes a long time to master this?