sentences:  Chaos Machines appear at gaming and science fiction conventions, where attendees are encouraged to create, modify, tune, and improvise new gadgets (stunts) for the rolling-ball construction.At each sitting, the machine is set up as a basic framework by the Machine Wranglers, then participants (Mechanics) begin to build tracks, install ball lifts, add stunts, and generally have a good time learning and problem-solving.Over time more sets are added, so the machine grows larger with each appearance.