Do you remember the last time you fully geeked out? You are about to. Universe Sandbox takes the joyous freeplay of Powder and such into 3D. Astronomical scales are laid out for you with a fully zooming and rotatable camera, trails tie knots and stream like ribbons, light waves pulsate at remarkably slow speeds, time is at your command. You can throw a star through the asteroid belt and see what happens. It brings out the awed child in all of us.
The game-like app comes with a set of "Fun Things To Do" which unfortunately does not include cocaine. Among them, creating a perpetual motion machine of moons orbiting the earth (which is a great demonstration of the cusp-of-complexity principle), crashing the Death Star into Endor, and smashing a bloc of moons like a billards deck. In the tradition of great indie games, some of the most charming things about Universe Sandbox are its bugs, which are actually just you tearing the system apart with outrageous variables. For example, speeding up time causes the physics calculations to lag behind the spatial adjustments, orbits flinging out of whack with cartoon-like kineticism, and you can put the thing to the brink of crashing. You could say the time-distortion effect is the simulation taking into account the computational fabric of the universe -- think about that next time you're stoned.
There's a lot more that could be done with this: galaxies, supersymmetry, gods with constrained abilities to warp gravity and shatter constellations, fractal multiverses triggered by chain reactions of black holes. But hey, I'll take it.