DDR is short for Dance Dance Revolution. It's a game series for PS2 and XBox. You have a mat, usually a cheapie plastic thing or you can buy a padded no-slip mat. When you start the game, in any more, arrows will appear on the screen. When they reach the top you have to step on the correct arrow on the mat, usually with the beat of the song. Depending on the level of difficulty there are a few arrows or a ton! Sometimes you have to step on two arrows at the same time. But it's still really fun. I barely felt tired, though I was sweating pretty good. My feet hurt, but that was after a half hour nonstop.
"I have spent far too much time on a scale that merely weighs your affect on gravity, not the depth of your beauty."