Never underestimate the power of fun. This month we play with two mind-bending puzzle games and a download that helps you show off and share the things you love.

A Numbers Game That's Only Logical

Newspapers across the U.S. have added the logic puzzle Sudoku to their pages. My local newspaper sacrificed "Dennis the Menace" to make room for it, and my train commute has felt shorter ever since.

Pappocom's Sudoku software lets you play the game on your PC or on printouts. A basic Sudoku looks like a nine-by-nine square crossword with all the spaces used. A grid divides the puzzle into nine smaller squares. Most puzzles use the numbers one through nine in the spaces (the word sudoku means "single number" in Japanese). Each puzzle arrives with some numbers already placed. Your job is to fill in the puzzle so that each number appears once--and only once--in each column, each row, and each small square.

If this sounds hard, don't fret. Pappocom's program offers puzzles in three levels of difficulty and plenty of help. You can pencil in tentative choices, avail yourself of hints, display incorrect answers, and erase mistakes. When you beat your average score for that difficulty level, warm applause cheers you on.

If you're good at the game, you can turn off the bells and whistles and move up to more difficult puzzles. You may find yourself choosing new fonts, symbols, and color palettes to make the time you spend with the puzzles even more enjoyable. And if you really, really like Sudoku, you can print several puzzles to a page and take them with you when you're away from your PC.

Pappocom's trial version stops functioning after 28 days. To keep using the program, register it for a $15 fee.

Puzzling from Every Angle

If you're ready for a new challenge--or if you find Sudoku's squares too restrictive--you may enjoy puzzles that use several different geometric shapes. With Classic Pythagorean Puzzles, you build complicated constructions out of basic shapes.

Similar in concept to Chinese tangrams--although employing different geometric tiles--Classic Pythagorean Puzzles sets out two small isosceles triangles, two larger ones, two squares of different sizes, and a parallelogram. On the right-hand pane, CPP shows a construction to build by rearranging the shaped tiles. It can be tricky, but it's a fun mental workout.

You control the tiles with either keys or a mouse. The selected tile shows in green, contrasting with the yellow of unselected tiles. When you complete a puzzle, the program displays a message of praise and laughs out loud like a delighted infant. Once you've mastered the basic one-person game, you can create Classic Pythagorean Puzzles for others to solve.

You can play with Classic Pythagorean Puzzles to your heart's content for 30 days. After that, it cost $11 to register the software and continue to hear babies chortle at your cleverness.

Do You Know What Imeem?

Blogs, photo sharing, instant messaging, and Internet forums are here to stay. Trouble is, it's hard to get all these things from the same service. Who wants to read four different privacy policies, learn how to use four different Web sites and/or software clients, and then try to get friends and family to join four different services? Imeem combines these elements into one free peer-to-peer service with an easy-to-use interface.

I installed the Imeem download and joined the service, both of which are free. It took just a few minutes to get up and running. I found it simple to navigate the attractive interface, which uses several panes as well as browser-like Back and Forward buttons. The pleasantly plain instant messaging window shows conversations with photos and word balloons, which is much more personal than the usual bizarre screen names. Setting up a "meem"--a sort of community area for a given topic, such as computer security or gardening--takes moments. All public meems and profiles are searchable in the interface, so I was able to search for puzzle addicts to invite to my brand-new Sudoku meem.

That said, your personal information doesn't have to be on display. The folks at Imeem tell me that the software client holds all the data in your profile and postings, so that information stays on your desktop instead of on their company server.

Imeem offers a very granular level of privacy. Like most community services, Imeem lets you choose whether you want to make your profile visible to the entire Internet, to other subscribers, to your friends, or to your friends' friends. In addition, you can mark items within your profile with the same levels. For instance, you could let the world know what country you're in, but hide your home state from anyone but other Imeem users. Then you could reveal the city to friends only. The same goes for your age, your photo, and your real name.

These levels of privacy extend beyond your basic profile. You can set up each "meem" as public or private. Suppose you'll discuss baseball with complete strangers, but you'd only share Grandma's jealously guarded recipes with family members. Imeem lets you have it both ways. Once you've joined or started a meem, you can stock it with forums and (in private meems) photo albums.

Targeted ads pay for the free service. Since all your info remains on your local machine, the ad servers don't keep a profile on you or save your information. With every visit, Imeem checks for your interests and decides what ads to show you.

Of course, you can use Imeem for work as well. Private meems are just like any group blog for coworkers. But while you're setting one up for your department, you might as well join my Sudoku meem, right?

PC World Senior Associate Editor Andrew Brandt contributed to this story.

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