I saw that demo and came to the same conclusion as you did.
I now think they were simply measuring the distance of dynamic objects from the focus point and then applying forces on those objects according the the square of distance rule. Using vectors would probably be the simplist way. There is a tutorial in one of the back issues of the magazines on vectors
In one way it is somewhat cheating but if you did create a mini black hole on the end of a stick the one thing most effected would be the player.
System
PIV 2.8 MZ 512 Mem
FX 5600 256 mem
