It revolves around a coffee percolator simulator.
You start with a volume - let's say a conical one - in which we place a number of spherical CoffeeBalls. Each CoffeeBall has a mass and position; a physics simulator ticks through each frame of the simulation, ensuring that all the CoffeeBalls are bunched down at the bottom of the cone.
Next, we add a number of WaterBalls. All WaterBalls have the same mass/radius, and all have an initial "concentration value" of 0.0.
The WaterBalls are dropped randomly in through the top (open) end of the cone, and the physics system takes over. WaterBalls do not collide with each other, but they do collide with CoffeeBalls - and when they do, a force is exerted from the center of the CoffeeBall to the center of the WaterBall. Not such that the WaterBall cannot overlap the CoffeeBall, you understand - just enough to stop it from ignoring the CoffeeBall completely.
For every cycle that the WaterBall overlaps the CoffeeBall, an "absorption" occurs. An absorption causes the WaterBall's concentration value to increase, and the CoffeeBall's mass/radius to decrease. The extent of the absorption is a factor of how much the WaterBall and CoffeeBall overlap, along with the WaterBall's current concentration value (to simulate saturation).
Eventually, WaterBalls collect at the bottom of the cone, which they are permitted to pass through. They collect in the bottom; some kind of summation occurs, to result in a total amount of brewed coffee, with a given homogenous concentration value.
Cool? Pointless? Worthwhile? What do y'reckon?
However, as a simple physics demo, I guess it's worth pursuing. If nothing else, it makes an amusing addition to a code portfolio. "Terrain engine, A* pathfinder, ...coffee perculator? WTF?"