The wall
The wall's line is the outline of what is already built, smoothed, wobbled, then fitted to the ground; it stops at the river and picks up on the far bank, and it is still standing in 1890.
A palisade and a wall segment are the circuit and nothing else. A defence commission on an ordinary plot inside the town is a guardhouse, with a lid, a door and a flag; the piece of rampart that used to stand in the market place defending nobody from anything is gone. The wall that goes round the village is drawn by wall.rs, and it is the only one.
The line is the built-up area’s own outline, smoothed, given a slow harmonic wobble, then fitted to the ground bin by bin: high ground and level ground preferred, the town avoided, the contour followed, water refused outright, so the line stops at the bank and picks up on the far side. It is built to the height of the eaves it is defending, with lower curtains, continuous walks and broad raised shoulders instead of isolated spikes, and gates where the streets go out.
Then the town outgrows it. The wall becomes an obstacle, the gates are torn open for carts, the ditch is paved over, and the ring road follows the wall. Two hundred years later you can see it in the street plan, and if you cut the ground open, in the stone.
In the code: crates/sim/src/city/wall.rs