My latest project is a game that uses music as the gameplay content. I use spectrum information to detect energy pulses in the music and use peaks to trigger emission of particles. The object of the game is pretty simple - collect the particles while avoiding the red boulder-thingies. Grabbing stars increases a score multiplier.
Collecting the particles, in addition to increasing your score, fuels three kinds of colored energy - shown by the three lines inside your circle. This energy can be expended to use a shield, give you a speed burst, or temporarily suck particles toward you.
There are also cooperative and competitive multiplayer gameplay modes. This is a mode where players are "bungied" together:
Here is a gameplay video:
