Picross is a Japanese puzzle akin to a wordsearch or crossword, only more math-based (so more like sukodu then). You are given a grid and a series of numerical clues and you have to shade in parts of the grid to make a picture using those clues. It starts out easy enough, once you figure out how the game works, but gets ever more cerebral when you decide on where the potential shading squares might be and where they definitely are. It's a bit like Minesweeper in that respect. It's impossible to describe without actually playing it, so my advice is to look for a ROM or check the link near the bottom of this article.
I contemplated turning this into a "Designing Genres" post, but there's nothing that can really be done to this genre, since the "gameplay" has basically stayed the same since the puzzle was invented. Instead, I'll talk about the video game conversions of this puzzle to date.
The earliest version to actually receive a western audience was the GameBoy title "Mario's Picross", which combined everyone's favorite plumber mascot with the world of Picross. Though actually part of a long series of GB Picross games, Mario's Picross remains to date the only Picross game to have been released outside of Japan. I've recently been playing Picross DS, which has various graphical features to assist you in playing the game.
First, and this is pretty cool, you have a puzzle "theme" (such as space or zoo animals) and you shade in special grids made for each theme. So for the space theme, the shaded squares become little airlocks that open/close. For the furniture theme, the whole grid is bubble wrap and you have to pop the squares that need shading in. The picture, once complete, turns into a little animation to help you identify what the image is displaying. Just little touches, but it makes the experience a whole lot more enjoyable. Designer subtlety is always something I try to keep an eye out for.
The final thing that needs to be said about Picross is that a western version actually exists in the form of "Griddlers", basically the same puzzle with a bizarre fast-food-type name. You can access Griddlers at their website, which is full of puzzles (and has a few demo puzzles if you don't feel like signing up): http://www.griddlers.net/
Not only are the grids significantly larger than anything the GB/DS games can handle, but they also experiment with different colors and shapes you can use, which can make the puzzles easier or harder depending on the picture. Each puzzle is rated by a computer "difficulty", which uses some kind of programming logarithm to decide how long it would take someone to solve the puzzle via logic (rather than just guessing what the picture will look like) and award you that many "points" accordingly. It tends to become one of those bookmarks you always click when you have five minutes free from work but still need to keep your mind sharp.
