What is stepmania?

If you are on this site, then chances are, you know what stepmania is. If you don't, then feel free to visit the main stepmania site.
To provide you with a brief description of stepmania, it is an open source rhythm video game. Arrows gradually scroll up the screen and are to be pressed when the reach the target arrows area. Users can create custom simfiles to play songs of their own choice. Online network play is also available at stepmaniaonline.
If you don't have the software, then you can download version 3.9 here [Mirror].
Version 4.0 [Mirror] is also available but is not officially released yet.