If you've ever stared slack-jawed at the swirling images of a music visualizer, check out Iridescent Configuration, a program where you take control of the lightshow.
Granted, there's no music involved (aside from whatever you play in the background) but you can play around in nine different visualizations, from an exploding orb of cubes to a particular cathartic visualization where you soar through demolishing blocks. In each one, you manipulate the rhythm, rotation, angle or flow with your keyboard and mouse.
Iridescent Configuration was created by Oliver Garcia-Borg, who describes it as "a sequence of vaguely intriguing experiments in motion, interaction, colors, shapes, and nonsense" that is "designed to give an unusual sense of agency." It's free to download for PC, Max and Linux, though you can donate what you will.
