Fun little thing a friend of mine showed me. Name is Audiosurf, and it lets you pick tracks from your music library to listen to and then constructs a puzzle-racing map based on the individual tracks. Several different modes of play, including just a general hit-these-avoid-these, a more complicated color-matcher which gives higher points for hotter colors (think the color wheel), and two-player cooperative play.
The track itself goes uphill during more mellow sections, and the more intense the music is the more of a downhill slalom you get hit with.
Found a video here of a song that Ryo once managed to get stuck in my head for days.
Edit: Looks like Tank is one heck of a roller-coaster.
