Skeleton¶

The engine is built whole before any of the city goes in. Every rule in the design runs from the start: the run-in, chance, both accounts, the Times, decisions, endings, the record and saving. Then comes the screen, and then the loops of the city, one at a time.

A toy city¶

The engine holds no fact about Ankh-Morpork, so it can be tried on a city of three boxes as well as on one of three hundred. The toy city has a reinforcing loop and a balancing one, one district, one building, one event and one ending, and every answer it gives can be worked out on paper. A save that replays to the same hour, a record whose totals equal the changes, and a loading check that refuses a box with no row in the box list mean the same thing on either city.

The screen is built on the toy city too. A person plays it through a term and has to be able to say what happened and why. If the toy city cannot show its two loops, the real one will not show any of its own.

The first loop¶

The first loop of the real city is Cockbill Street’s, from the homes page: the pump stops, the street does not complain, and the Palace finds out late.

It tries most of the design at once. The pump is a building and the Shades a district, so it crosses two levels. The failure is an event. How long the Palace takes to notice depends on trust in the Shades, so it runs through what the Palace knows. Press attention builds gradually and the repair arrives all at once, so both kinds of delay are in it. The Times reports it, mending the pump is a decision, and at the end the record has to explain why trust fell in the Shades.

Each loop after it goes in the same way: numbers for its arrows, its events, headlines and story, its trial, and its page’s claim held on the seeds. The Palace’s loops come second, so that political capital and the treasury can end a term.

Done means played¶

A loop is in when someone playing sees it. For Cockbill Street that means a pump stopping, the Palace hearing nothing for days, trust in the Shades falling, the Times arriving, the repair, and an ending that says what happened and why. A test on the core shows the parts connect. Only a game shows whether players can see the loop.