Steve Jackson’s Chaos Machine is, to quote the convention program book, “a giant communal build-it-yourself project that’s a cross between an erector set, model trains, a pachinko machine, a jungle gym, and, well, a Chaos Machine. Help unpack the parts and build the initial framework people will add to all weekend.”
Here it is being built in the Linucon hotel lobby. It has tracks for little balls to roll, and moving belts, like the yellow belt in the foreground, that hoist them up.
The congoers could amuse themselves with it in two ways. First, they could assemble it from a million of small parts like a giant 3D puzzle. Then, once it had been built, anyone could reconfigure it any way they liked, by moving some belts, tracks and pieces from one place to another, and play with it throughout the convention. You played with it by rolling the balls down the tracks. The machine also has a little basket attached to it, as one can see in the bottom picture; you might want to roll the balls in such a way that they would fall into the basket, and reconfigure the tracks to that purpose. But you could invent your own goals and move the parts around accordingly. I guess that’s what makes it a Chaos machine.