The article discusses the development of xkcd's 'Machine', a collaborative Rube Goldberg machine builder game, created in three weeks by a team of developers. The game allows users to create and submit their own machine tiles, which are then moderated and connected to form a large machine. The developers had to make design decisions to balance player expressiveness with the need for a functional and engaging game. The game's architecture and physics engine are also discussed, including the use of snapshots to create a seamless experience.