Urban layout — adjacency & the unrest floor

Layout is the third economic axis, next to what you build and when. Each age declares an urban style table — a handful of adjacency rules that pay bonuses for period-true placement (dwellings ringing the campfire, the kiln beside the clay pit) and, from the Medieval age on, express bad layout as a bounded unrest floor. Nothing is stored: every effect is re-derived from where things stand.

How a rule reads the map

• One distance metric. The Chebyshev gap between footprint rectangles: gap 1 = touching, diagonals included ("beside"); "within R" means gap ≤ R. Terrain objects count matching cells in the ring around the subject.
• Subject → Object. A rule's subject (who benefits or suffers) and object (what it wants nearby) are each any-of lists — "Dwelling or Bulwark", "the hearth or a cistern". A matcher is satisfied once per subject when the union of its alternates yields enough matches — a dwelling beside two smog sources is smogged once, not twice.
• Unless. If any unless matcher matches, the rule is suppressed — the single mitigation mechanism (a well against miasma, a union hall against smog). It also powers negative-space rules: an object of "always" plus an unless of "a dwelling beside me" wants empty surroundings.
• Stacking. Default cap 1 (a rule pays once per subject); a rare rule opts into counting distinct objects up to its cap. All effects are flat integers on 1–4/tick bases — +1 is a real +25–100%.

The three effect channels

• +Output — added in the tick's production fold, on top of the construct's base output, clamped to caps like all production.
• +Housing — raises HousingCapacity only. Never shelter: the Upheaval's shelter math stays structural, so layout cannot inflate survival through two channels.
• Unrest floor — bad layout holds effective unrest at max(stored, floor), with the floor capped at 300/1000 → worst case exactly −15% survival at the Upheaval. Zero per-tick unrest from layout: a fed, housed town with the worst layout sits at its floor and never spirals.

What the floor actually costs you

This is the one place layout can hurt, so it is worth being exact about how much. A floor rule charges its penalty once per violating subject — per smogged terrace, per crowded cottage — and the total is clamped. Then the Upheaval reads the higher of your stored unrest and that floor, and applies the same decline penalty it always has.

• The floor is a floor, not a tax. If your stored unrest is already above it (you've been starving), the floor changes nothing — it only ever stops unrest going lower than your layout deserves.
• It never spirals. Layout writes no per-tick unrest, so it cannot feed the starve/recover loop. A fed, housed, badly-zoned town sits at its floor forever and dies of nothing.
• Every floor rule has an answer in its own age — machine-linted, no exceptions: the Medieval well or infirmary suppress foulden; the Victorian Union Hall suppresses smog; Modern nimby answers to free distance — the whole point of a zoned grid — or, for the blocks that won't move, to the Civil-Defense Bunker. You are never asked to solve a problem the age can't solve.
• 15% is the ceiling on ignorance. A player who never thinks about any of this loses at most 15% of their survivors at one Upheaval — and the progression contract proves the naive fresh start still closes every age inside one hourglass with all floors live.

The frontier — where you may build

Placement is bounded by a derived reach envelope, and the shape of that envelope is the heart of the redesign: you make your world bigger by founding cities, not by paving roads. Three things grant reach, and only three.

• Every city centre radiates a SeedRadius disc. The valley origin commands one from the very first tick — the disc is anchored at the origin itself, not at any placed building, so it exists before you build anything. So does every new hearth you found out in the wilds (see Arteries, below). A second centre is a second disc of fresh buildable ground, so founding compounds your reach rather than nudging it out by one building.
• Every live construct adds a ChainRadius bubble. Each thing you place extends the envelope around itself, so a city grows in tendrils from its own edge. Pack buildings densely and the bubbles overlap into solid ground you can keep building on; string them out thin and you reach no farther than the last one.
• An artery — and only an artery — throws a RoadRadius band of reach along its length. The paved gaps between your buildings (the fabric, below) carry no reach at all. This is the correction the redesign turns on: a dense block organizes a city but does not enlarge it — otherwise every neighbourhood would be its own frontier and expansion would once again just happen as you build.

A tap beyond the frontier is refused (OutOfReach — "Beyond the frontier — build closer."); demolition never retro-invalidates (reach is judged only at placement time), and each age's seed bypasses the check entirely. Everything here is re-derived from where things stand — nothing is stored, and a loaded save never re-checks reach.

• The Expedition Waiver — the anti-wedge guarantee. Terrain-gated kinds (the woodcutter, the farm, the colliery…) check reach with +4 slack — harvest crews walk out. If no legal placement of that kind exists anywhere inside the slack envelope, the reach check is waived for that kind everywhere until one does: the expedition founds a camp at the treeline ("No forest within the frontier — expeditions may found this beyond it."), and the camp then anchors the next chain step. Terrain reachability is unconditional by construction — no seed or Upheaval history can wedge the economy behind the frontier.
• Ruins are beacons, not anchors. Constructs carried from an earlier age persist wherever they stand — even beyond the frontier — but anchor nothing until reclaimed: a live construct within ChainRadius of a ruin snaps the frontier around it. Building a tendril out to an ancestor's longhouse is how the old world comes back into reach (and reclamation cascades — ruin by ruin — are intended). An unreclaimed ruin's streets count for nothing either: any paving an old ruin created still renders (old roads to old places is the point), but carries no reach until the ruin is reclaimed — otherwise the dead world's streets would quietly hand you the frontier the beacon rule withholds. Reclaim the ruin and its streets carry reach like any other.
• Derived, never stored. Reach, waivers, and reclamation are pure functions of the placed set + terrain — the save format is unchanged, and loads never re-validate reach: placements restore verbatim, wherever history put them.

Two kinds of street — the fabric and the arteries

There is no pave verb; the sim never draws a road you didn't earn by placing buildings. In the Stone age the network is desire-path trails — and they are invisible: the derived lines exist (villagers prefer walking them, and the rules read them like any other street cells) but the board shows only wilderness. Watch the villagers and you can see where the trails run. Stone has no urbanism, and that is the whole point of the age — visible infrastructure first arrives with Bronze.

From the Bronze age on there are two kinds of street, and they do different jobs.

• Fabric — the paved gaps between buildings. Site two buildings within an alley or two of each other and the negative space between them becomes a street: you don't draw it, you leave it. Build a dense block and its streets appear for free; scatter your buildings and you have no streets, because you built no town. Fabric organizes a city but does not enlarge where you may build — it carries no frontier reach (above).
• Arteries — the roads between cities, and your one expansion verb. To grow onto new ground you place a gate on your city's edge and found a new hearth — a second city centre — out in the wilds within the age's reach; the sim derives the artery that connects the two. It is an ox track in the Bronze age, the king's road by the Medieval, a railway by the Victorian, a motorway by the Modern — and it is the only street that extends your frontier, throwing a band of reach along its length. Each age's road tech reaches farther than the last (roughly a dozen tiles in the Bronze age, up to thirty by the Modern). (A founded city is fully live this age; carrying founded cities across an Upheaval into the next age is future work — for now each age raises its cities anew.)

• Geometry is the era. The router pays an age-tuned price for turning and for crossing hills or forest, so the roads it actually draws — Stone's trails and every age's arteries — straighten as civilisation advances: Stone paths meander with the land for free, Victorian cuttings ignore hills, Modern avenues pay so much per turn they run die-straight. (Fabric needs none of this — an alley's shape is just the shape of the gap the buildings left.) Watch the arc in the table below, straight from the sim.
• "Build on the street — your own street doesn't count." Street-adjacency rules (the Victorian terrace's frontage bonus, +1 Housing) ask two questions of a cell, and both must answer yes. Is it a street? — paved, and not under a building. Buildings are never streets, so standing beside an older building earns nothing; the rule wants a real street. And did it exist before me? — every cell a building's own arrival created is stamped with that building's turn, so a street you made by placing yourself can never pay your own bonus. Build a terrace along an existing street and it qualifies; a lone terrace whose only paving is the alleys it just formed doesn't; a terrace merely beside an older building doesn't; and paving that arrives later doesn't retroactively pay either. The placement preview always shows the truth: a ghost is evaluated against the whole current street network, exactly what committing right there would earn.
• Streets are incentive, never gate. No construct requires a connection to function; a disconnected building works at full base rates. The network's only mechanical reads are artery frontier reach (above) and street-adjacency rules like frontage — fabric alleys pay adjacency bonuses but never carry reach.
• Derived, like everything else. The network re-derives from building positions in Id order — saves store no roads, and the same placements always grow the same streets.

The six styles — the arc's second spine

Every playable age now declares a style, and read in order they tell the same story the ages do: The Hearth Circle (huddle around the fire; the wilderness is the wall) → The Courtyard Well (knot around hearth and cistern, farms pulling toward water) → The Walled Close (density pays — but crowding away from clean water breeds pestilence: the first age where layout can cost you) → The Piazza (the ring of façades; bonus-only, the arc's breath) → The Iron Terrace (frontage rows against the smog shadow) → The Zoned Grid (cars let you separate, so the game asks you to).

The Iron Terrace — the one real dilemma

Most rules reward you for noticing them. The Victorian table is the one that makes you choose, because two of its rules read the same radius in opposite directions. Labour pays the colliery +1 Coal for having homes within R2 — the pit needs hands. Smog charges those same homes +50 unrest floor for being within R2 of the pit. Site them together and you buy throughput with survival; segregate them and you get a clean Upheaval and a slower age.

The Union Hall is the paid reconciliation, and it costs Goods 12 + Steel 4 — the age's bulwark, the thing you were saving for anyway. So the question is real rather than a knowledge check: spend the Steel on the hall now, or run the pit dirty and eat the floor? Both answers are legitimate; the sim pins all three rows above as test fixtures so the tradeoff can't quietly evaporate under a tuning pass.

Per-age style tables

Straight from UrbanStyleCatalog — the same rule objects the tick evaluates. Watch for the shapes that only appear once: Medieval care is the only rule that stacks (up to ×4, parish coverage); Medieval openfield and Modern subdivision are negative space — they want nothing nearby; Modern electrified pays whatever the subject makes, so siting the power station tunes the whole industrial base at once.

Can I buy my way out of a bad layout? (not yet)

Nothing in urbanism is gated behind Knowledge, and that is deliberate. Every rule and the frontier itself are always live, because the progression contract insists the free construct set works at zero owned nodes — layout skill can never become a thing you must purchase before the game is survivable. Two Knowledge leaves are nevertheless declared for later: Surveying (+1 ChainRadius — tendrils reach farther) and City Planning (the spatial unrest floor halved). Both are reserved and inert: visible in the web, unbuyable, with no effect wired. They exist so the promise is legible now and the numbers stay open — turning them on is a balance decision of its own.