Have you come across Picross yet? It is sort of like Sudoku, which came from nowhere and nearly over night became this huge success. Now it feels like everyone (usually over the age of 40) is doing Sudoku instead of the good old cross-words. This is a common phenomena with hypes from Japan, they just sweep over the world and find fans everywhere. Everyone knows what Sudoku is, and only in sweden we've got several magazines devoted solely to Sudoku. Not as many people have heard about Picross however, eventhough it is closely related to Sudoku.
Picross is like Sudoku in that it's about mathematical problem solving over a grid. The main difference about Sudoku and Picross is that Sudoku is only about aligning numbers correctly, after a set of rules, while Picross is about aligning markers correctly, after a set of numbers. The end result isn't just a grid filled with numbers, but a grid filled with markers that form a picture.
I never got the fun about Sudoku really. I tried it but to me it was quite boring just repeating the exact same procedure of aligning numbers. Although the procedure is repeatable in Picross as well, the end-result never is. Your reward will always be some sort of picture. Weee, pictures!
I've only found one small magazine in sweden which solely revolves around Picross problems, called "Japanska Bildpuzzel", although I know some of the Sudoku magazines also include Picross. There are also video/computer games about Picross, just as with Sudoku. I am currently ending every evening with some Picross puzzle solving on my NDS (the games called "Picross").
Just as with Sudoku, the first time you see a Picross Puzzle you don't really get much about how to solve it. And just as with Sudoku, the rules are quite simple to learn but difficult to master. The difficulty levels of the puzzles can vary between very easy to very difficult of course, depending on the size of the puzzle and the positioning of the markers, as some markers are more favorable to have than others in terms of difficulty.
I'll try to explain the rules, but it'll probably sound really confusing until you try it for yourself, and you really should! It's great fun!
The Picross Puzzle is made out of a grid composed by X*Y boxes. They can of course be smaller or bigger, sometimes the same height and width but don't have to be (the above picture is from a 35*45 grid Picross!). Along the X and Y axis are a set of numbers that tell you how many boxes are to be marked in the grid, but not where and that is the tricky thing about picross (just as in Sudoku where you know a number is to be somewhere in the grid but not where exactly). Where you should mark is determined in relation to the other marks. So if the grid is 15 boxes wide and the Y axis says there should be 3 boxes marked on row 14, you don't know which of the 15 boxes that should be marked, just that 3 of them total will be. If it says row 15 should be marked for 15 boxes it's simple, because that would be the entire row. If it says row 6 should be marked for 10 boxes you can mark the middle 5 out of the 15 because no matter where you end up having to put the 10 marks, the middle 5 will always have to be among them.
Well as you can see this really just turn out to be confusing. The best thing is to check out the internets for some Picross and try it out for yourself. As you solve them you constantly learn new tricks to make it easier. I found one page which seemed to have both a tutorial and a huge library of puzzles, so it might be a nice place to start out. Personally I solve my Picross on my NDS or by hand in the magazines (as you can see in the picture).
So get started and tell me what you think ;)