Look it up?

You can do that but I am telling you this is a game that is so addictive that you will be playing it nonstop, especially since you can download new puzzles, perform in the daily challenges, and of course, play others over Wi-Fi.

There is a reason GI and others have included Picross DS as one of the 50 best games in 2007...not to mention it only costs 20 dollars.