Who would've thought that 10 years after its introduction, the Dance Dance Revolution franchise would still be going strong? Today DDR celebrates 10 years of getting kids off their butts and gyrating and stomping their feet in tune to songs no one has ever heard. At that age, the game now has the rare distinction of being older than most of the people actually playing it.

If you've never seen DDR in action you don't know what you're missing (check out this video, or search for "DDR" on YouTube for much, much more). Though dozens of versions exists -- and numerous knockoffs have come out, too -- the game is simple in concept: Players jump around on four light-up pads in time with the music. Miss the pads or dance off-beat and it's game over. It's harder than it sounds.

DDR was a real milestone for video games, ushering in the rhythm category in earnest and ultimately paving the way for music titles like the Guitar Hero and Rock Band series. It was also critical in reviving arcade culture, which had been withering for years. Once DDR came along, watching other people play video games again became a spectacle that could draw major crowds. The machines are enormous, and still they are surrounded by gawkers when someone really good takes the stage.

Finally, it can't be underestimated how much DDR has contributed in getting kids to exercise. Even grown-ups have gotten in on the calorie-burning action (here's one woman who lost 50 pounds playing DDR and telling her tale on Jeopardy!). Now who says video games never did anything good for humanity?

In related news, the milestone shooter Half-Life also celebrates its 10th anniversary this week. While not exactly the watershed title that DDR is, Half-Life remains one of the best-selling PC games ever, and its game mechanics and subdued story have had a lasting impact on modern game design. To celebrate, the original Half-Life is just 98 cents if you buy it via Steam. Alas, a DDR arcade machine will still run you about 16 grand. (It's also available for just about every game console, too.)