Silo Simulation — Project Overview

SILO is an agent-based simulation of a self-contained underground colony where autonomous people live out their lives—working, forming relationships, raising families, aging, getting sick, and electing their own leaders.

Survival is never guaranteed. The colony must produce food, maintain air and water systems, manage waste, control crime, trade with the outside world, and endure disasters and epidemics. Livestock and a complete wild ecosystem live alongside the human population, creating an interconnected environment in which people, animals, resources, and infrastructure all affect one another.

The simulation can unfold in real time, letting you watch the colony develop day by day, or run in fast-forward mode to simulate years in seconds. Multiple independent silos can link together into a shared mesh, developing separately while exchanging migrants, food, medicine, water and materials — a web dashboard page shows the whole mesh as a live graph of what's moving between them.

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People & life cycle

Each person has an age, sex, race, religion, appearance, job, health, happiness, hunger, energy, reputation, personal money, relationships and family.
Personality: two traits set at birth and partly inherited from a parent — constitution (how well they hold up under strain) and temperament (whether they tend to be happier or gloomier than average).
Happiness settles toward the level a person's life supports. A partner, a job (or being a child or retiree), being fed and rested, close coworkers, home comforts, good standing and fair weather raise that level; hunger, exhaustion, outages and disaster clean-up lower it. Each day happiness moves about a tenth of the way toward it, with a little day-to-day noise. A one-off blow — jail, a death, vandalism — fades over a couple of weeks, and a lasting strain (poverty, Silo Syndrome, bad sleep, toxic air) keeps someone lower for as long as it lasts. A partnered worker usually settles around 75–80, children around 60, and silo averages land around 65–75.
Life cycle: birth → childhood → apprenticeship (14–17, reduced output) → adulthood (18+) → retirement (75+, changed by some presidents) → death from old age, illness, starvation, violence or disaster. Under a Workaholic president apprenticeships start at 12 (as Farmers, Ranchers, Fishers or Sanitation Workers) and retirement moves to 83.
Education: children who grow up with enough Teachers become up to 15% more productive as adults.
Births slow down in three realistic ways:
Family planning — couples slow down after two or three children.
The birth lottery — as in the Silo books, each silo is built for a head count, and birth permits are issued against the places left. With a tenth of the places free, permits are given freely; as the silo fills they thin out to a trickle (the lottery). A baby on the way counts as a place taken. The log says when permits go to the lottery and when there is room again.
Hard times — fewer births while water or food is short.

The head count grows. New living quarters are fitted out a little every day the silo isn't short of food or water — 1% a year (SILO_CAPACITY_GROWTH_PER_YEAR) — and the log notes every ten new places. So the population keeps growing, at the pace the head count sets. A silo that was already running starts with a head count equal to the most people it has held in the last three years; a brand-new silo is built for two and a half times its founders. The editors show the places taken and can set the head count (edit-colony --set-capacity N, or "Head count (places)" in the GUI's colony dialog), also while the silo is running; the lookup's silo status and the health check's per-silo table show it too.

A place is a place. Someone moving in from another silo takes one of the places birth permits are issued against. Each silo publishes how many places it has free, and people looking for a job or a happier life, and recruits, only move where their whole family fits; otherwise they stay home ("🛂 … hoped to move to Silo K, but it has no room for a family of 4"). Refugees, fugitives and exiles don't ask, so a disaster next door can still leave a silo over its head count; its permits then stay at a trickle until the head count catches up.

Crowded with refugees. A silo that refugees have taken over its head count is crowded — fully so at 25% over, and no worse beyond that. Only refugees still living there as guests count (by as many as the silo is over, and no more than there are guests), so a silo with no refugees is never crowded, however full it is. Illness spreads faster (up to half as fast again at full crowding). Once the crowding is noticeable (2.5% over or more) unrest stops settling and grows every day instead, by up to 0.8 points a day at full crowding: on its own, a silo 13% over reaches strike level in about ten weeks and riot level in about four months. It ends as the guests go home or settle. The log says when it starts ("🛏️ With the refugees the silo is over its head count — 224 people in room for 198") and when it is over; the lookup's Refugees line shows it. In a 300-day test with six silos that all started exactly full, 11 of the 12 families who moved for a job or as recruits had gone where there was no room; after this change, none did.

This replaced a rule that limited permits by the share of children (from 35% to 50% under 14). That rule held the mesh at 46% children with a median age of 17 and no ceiling on growth: nearly every adult had a job and one post in ten still stood empty.

Children eat and drink less: under-5s need about half of what an adult does, ages 5–12 about 70%.
Poverty: a child is only poor if their household is; orphans are provided for by the colony. A married or settled couple shares its money: each of them is poor only if the two together have under twice the line ($700).
Marriage and partners: a couple does not have to marry. After a couple of months together their moment comes: two couples in three marry, and one in three settle down as partners instead — together for good, but unmarried.
On marrying, the wife takes the husband's surname. A settled partner keeps her own.
Children take the father's surname either way.
A few settled couples marry after all, years later (about 3% of them a year).
A widow's birth surname is restored.
Breakups & divorce: dating couples split up fairly often. Married couples rarely do (around 2% a year): unhappiness, poverty, hunger and colony crises raise the risk; young children and long years together lower it. Settled partners are weighed the same way and part about twice as often as a married couple in their place would. Someone whose husband or wife leaves the silo without them (escapes from jail, say) is single again and free to marry.
Out of work: an unmarried couple (dating, or settled partners) is under strain while a partner of working age has no job. They are one and a half times as likely to part, and twice as likely when neither has work. Marriages are not affected. Someone retired, in jail, on the run or serving as president does not count as out of work. When the lack of work is what tipped a couple apart, the day's log says so and the silo keeps count.
Immigration and emigration: a small trickle of newcomers arrives (more under an Immigration Champion president, none under an Isolationist), and people leave when they're unemployed, unhappy or in hard times — taking their partner and children with them. In a mesh there is nowhere else to go but another silo: they move to the neighbour with the most room and breathable air ("🚶 ... has left for the other silo -- seeking a new life in Silo E"), and if there's nowhere to go that day (no room, no safe neighbour, the network down or the transit link cut) they stay. Nobody simply vanishes. A silo running on its own still loses them "for a new life elsewhere". A family never splits over a move: nobody goes while their partner is held here (the president, in jail, on the run, on contract) or away on loan, while away on loan themselves, or while a child of theirs is in jail and would be left with no parent.
Life stories: each sim keeps a short record of their life's milestones: birth or arrival, jobs and shops, marriages, settling down unmarried, divorce and widowhood, children, jail, injuries, diagnoses, the presidency, moves between silos, retirement and death (up to 24 entries: the first few plus the most recent). People who were alive when stories were added start with what the records showed at that point. When someone with a full life dies (25 or older, with at least two notable facts), the activity log adds a short clause to the death line, and the newsletter prints an obituary (at most 3 per issue, the most notable lives). Read anyone's story with A <name> story in the lookup tool.

Sleep & night shifts

Night shifts: round-the-clock jobs (Guards, Water and Atmosphere Technicians, Firefighters, Doctors, Engineers) keep a night crew, rotated every four weeks. Parents of a new baby are excused.
Sleep quality: each night, how well a sim sleeps depends on real causes — working nights, a baby at home, stress, hunger, illness, recovering from an attack, bad air, a power outage, a storm, or old age. Good sleep restores energy; tired workers are a little slower, and a really bad night costs some happiness.
Night log lines describe what actually happened: someone on the night shift, someone kept up by a baby or a fever, or people who slept soundly.
Visible bedtime: in both visual views, sims leave the residential floor around dusk (children first) and return at dawn. At night only the night crew, bad sleepers and a few night owls are out.

Personalities

About half the sims have one personality trait (never two), shown as "Personality" on the lookup page and on a sim's card in the 3D view. It is settled the first morning they are in the silo; a child takes after a parent four times in ten. Each trait only shifts the odds of things that already happen, never makes something certain:
Ambitious: three times the odds of winning a presidential or shop election; reaches for any open skilled post (if their own job can spare them), three times as often as others switch jobs; after a year as a Porter or Sanitation Worker their happiness settles 5 points lower until they move up.
Cautious: never asks the bank for a loan, however poor; never panic-sells in a fund crash; saves at the bank half as often again.
Gregarious: pairs up twice as fast and gets twice the lift from a festival, but "nobody close" weighs twice as heavily toward a breaking point.
Volatile: a short fuse (the "temper" strain, as for someone born with a dark temperament); four times as likely to start a fight after too much to drink; three times the weight to be among the rioters; at a breaking point they rarely do something quiet.
Steady: spells of Wall Fever and Winter Grey, and grief, last 0.6 as long; half as likely to reach a breaking point; festivals and shop treats lift them half as much.
Nurturing: a newcomer working beside one learns the trade in three quarters of the time; they take a loss 1.3 times as hard.
Honest: never steals (theft, burglary, shoplifting, fraud) and, as a Guard, never takes a bribe; as a Banker never skims; a false rumour about them is cleared completely; with one in the records office or at the network consoles, a crisis the administration hides is half as likely again to leak.
Curious: pokes about the lower stores -- each one has about a 15% chance a year of turning up a crate of old parts (15-50), or now and then a forgotten Founder Crawler or Walker, broken until the Machinists get it going ("🔍 ... found a Stair-Crawler under tarps in the lower stores"). But they want to see out: Wall Fever, and its spells, come 1.5 times as often, and at a breaking point they are twice as likely to go for the airlock.

People who work the same job slowly become friends; a close friendship makes the news and boosts happiness about as much as having a partner.
Best friends: an especially strong bond earns its own announcement.
Mentors: an older coworker with a strong bond mentors a younger one, boosting their productivity.
Rivalries: personality clashes between coworkers can boil over into altercations, or be patched up.

Jobs & the economy

Eighteen jobs, each needed at a share of the population (Teachers instead at one per 15 school-age children, 5–17): Farmer, Rancher, Fisher, Doctor, Pharmacist, Engineer, Teacher, Guard, Atmosphere Technician, Structural Engineer, Firefighter, Machinist, Water Technician, Sanitation Worker, Porter, Archivist, IT Operator and Banker. Each has a real effect — food, animals, fish, health, medicine, power, education, crime, air, seals, fires, components, water, waste, carrying, secrecy, the network or loans. Together the posts come to 69% of the silo's head count.
Sanitation Workers are the lowest-paid job ($4 a day, half a Farmer's wage). They need no training, so anyone from 14 up to retirement can take it. They do most of the everyday waste work.
Porters (4% of the silo, from age 16, $6 a day, no training): there are no lifts, so every kilo of food, medicine, sugar and spare parts goes up and down the central stair on a porter's back.
Goods on the stairs: the share of the day's goods that reaches the stores the same day is the porters' strength — porters at work against their posts (one on strike, in jail or home sick carries nothing). That covers the harvest, the ranch and the catch, medicine and parts made, deliveries from other silos and imports. The rest waits on the stairs, and each morning the porters bring down the same share of what is waiting. With every post filled nothing ever waits; at three quarters strength about a third of a day's goods is always on the stairs, at half strength a full day's, at a quarter three days'.
With no porters at all people still carry a fifth themselves.
Slower work: farms and the machine shop lose up to 10% of their output with no porters (2.5% at three quarters strength, 5% at half), because seed, tools and stock stop reaching them.
What it means: a short-handed silo has less in its stores than it has made — which is what counts for a food or medicine shortage, for what it can sell, and for when it asks neighbours for help. Goods on the stairs do not spoil and are not lost.
In the log: "🪜 The porters are short-handed: a third of today's goods are still on the stairs." when their strength falls below 70%, and "🪜 The porters are back at strength -- the stairs are clearing." once it is back to 80%.
Stair-Crawlers: a silo may have one or two hauling machines (see Robots); each does the work of 4 Porters, and the stairs need that many fewer Porter posts.
Archivists (1% of the silo, at least one; from age 20, $14 a day; a skilled trade) keep the administration's records in the records office, and keep what it has decided not to announce out of sight. See Censorship, under Presidency, for what happens when the office is short-handed.
IT Operators (1% of the silo, never fewer than two posts; from age 20, $16 a day; a skilled trade) keep the silo's servers, sensor relays, terminals and phone lines running. The network goes down in two ways:
Nobody at work: with no IT Operator at work that morning (posts empty, on strike, ill, in jail) it is down for the day, and comes back the first morning one is at work again.
A crash: a short-handed crew risks one each day — up to 2% a day, falling in step with the crew's strength to nothing when every post is filled by an experienced operator at work (a beginner counts for 70%; with one of two operators away it is 1% a day). A crash takes 2 to 4 days to put right, and a day only counts while someone is at work on it.
While it is down the silo is cut off from the mesh exactly as with a cut transit link: nothing is arranged with the neighbours and no people, goods, crews, teachers or stock trades go in or out. Neighbours still hear from it and wait; anything already in the mail arrives when the network is back, and people on loan stay where they are until then. The administration also loses its hold on the news: see Censorship, under Presidency.
Left alone: a silo that has never had an IT Operator (the rules start the day after its first one is hired), and any silo of fewer than 40 people — too few to have a network to speak of, so founders and the survivors of a collapse are not also cut off from help.
In the log: "🖥️ The servers have crashed: the network is down and Silo A is cut off from the mesh until the IT Operators get them back up -- about 3 days.", "🖥️ No IT Operator is at work: the network is down ... until one is back." and "🖥️ The network is back up after 3 days."
Essential jobs come first when there aren't enough workers: 1. Keeping people alive — Water, Farming, Doctors, Air, Power. 2. Important — Ranchers, Fishers, Structural Engineers, Firefighters, Guards, Pharmacists, Sanitation Workers, Porters, IT Operators. 3. Everything else — Teachers, Machinists, Archivists, Bankers.

New workers fill essential jobs first, then every job gets a fair share. People only switch jobs to rescue a more essential job that's badly short, or to leave one that's well staffed.

Sharing a shortage: a young silo has more posts than adults (job targets count everyone, babies included). The vital jobs are staffed first and trained specialists stay at their trade; Ranchers, Fishers, Sanitation Workers, Guards, Firefighters, Teachers and Porters share what's left. A worker moves from the better staffed of these to the worse staffed, but only if that brings the two jobs closer together, so nobody shuttles back and forth. Before this, Guards and Firefighters sat near half strength while the others were at 80%.
Surplus workers move on: anyone in an unskilled job with more workers than posts (a small silo's fourth Teacher for one class) may take any open job they qualify for.
Job experience: the ten skilled jobs (Doctor, Pharmacist, Engineer, Structural Engineer, Machinist, Atmosphere Technician, Water Technician, Archivist, IT Operator, Banker) take time to learn. Someone new works at 70% and improves to full over about two years on their own, or about one with an expert to learn from (80%+ experience): a working coworker in the same job, someone in the silo who mastered it and has since moved on (to another job, a shop, or retirement; not while in jail), or an expert lent by another silo. Experience is kept when changing jobs, and migrants bring theirs with them. Founders, and everyone working when this was added, count as fully experienced. Reaching expert level goes into the sim's life story. When a skilled trade is new to a silo that already exists (the Archivists, the IT Operators), whoever is in it on the first day anyone is starts fully experienced: they have been keeping the records all along. Later hires start as beginners.
Know-how loss: a silo's know-how in a skilled job lives in everyone there who has mastered it, whatever they do now. It is lost only when the last of them dies, leaves the silo or is away on loan; an expert who changes jobs, takes over a shop or retires keeps it alive (the log notes "No experienced Pharmacist is at work now, but ... still knows the trade and can teach newcomers"). When it is lost the log and newsletter say so, and new workers learn at the slow rate. It's restored, with a log line, when someone new masters the job or someone who already knows it arrives or comes home. In a mesh, a neighbour with at least two experts in that job may lend one for 90–150 days to teach, once the know-how has been lost for 30 days and someone there is at work in that job to learn it (a teacher isn't sent to an empty post; a small silo whose people are all needed in other jobs just goes without, the Mentor Walker standing in, until it grows). A lent teacher teaches full time: a beginner masters the trade in about 100 days with one (instead of about 290 with an expert coworker), and the teacher goes home as soon as someone has, without waiting out the loan ("… has gone home to Silo M -- our Pharmacists know the trade again"). Experts thinking of moving go there first (see the know-how pull under Cross-silo migration). Lost know-how shows in the lookup tool (the silo status, and Experts and Avg skill columns in A jobs, which also say when the know-how is "kept by N who used to do it"), each sim's Experience line, the mesh map (an amber KNOW-HOW LOST callout, and pink arcs for experts sent to teach) and the health check. The editors can set a sim's experience (CLI edit --experience 0-100, and a Job experience box in the GUI).
Contract hires: a skilled trade with only a person or two in it (in practice the Pharmacists, at 1% of the silo) used to keep its posts empty: the young already have a job by the time they are old enough, job switching only fills posts more than half empty, and no neighbour has one to spare. Now, when a skilled job has an empty post and fewer than three people in it, the silo signs up one of its own people, one a day:
Who: anyone out of work first; then someone in an unskilled job who has already mastered the trade; otherwise someone from the best staffed unskilled job that can spare them. A job can spare someone if it stays above its tier's floor or, when it is no more vital than the hiring trade, if it ends up no worse staffed than that trade is now. They must be old enough for the job, at least five years short of retirement, and not the president, a shop owner, in jail, a fugitive or away on loan. Among several, the best schooled gets it.
Bonus: $500 from the treasury to the new hire, only while that leaves the treasury above its reserve (three months of wages, or $20,000 if more; see Wages).
Contract: for five years (1,825 days) they can't be moved to another job (by job switching or onto the lathes in a parts shortage), take over a shop, stand for president, or leave by choice (emigrating, moving to another silo, being recruited away); a partner on contract keeps the family from leaving too. Death, disaster refugees, exile and being lent to another silo still happen. Jail and retirement end the contract; a seal-emergency draft does not. A contract doesn't travel to another silo.
Where it shows: a log line when it is signed and when it is served out, the sim's life story, a Contract line on the sim and "N on contract" in the jobs table of the lookup tool, and both editors (a duty line on the person, a Contracts line for the colony).
Settings: CONTRACT_THIN_TRADE, CONTRACT_BONUS, CONTRACT_DAYS.
Automation: steady Engineer staffing builds up a bonus of up to +75% on farming and power. Farm machinery needs power, so the farming bonus shrinks when power is short and stops while the reactor is down.
Education: steady Teacher staffing builds a bonus of up to +30% on farming and ranching.
Personal money: everyone earns a daily wage (Doctors earn about 2.5x what Farmers do), creating rich and poor. Wealthier people spend on comforts and are happier; poverty brings hunger, unhappiness, crime and unrest. Money passes to a partner, then children, when someone dies. Unemployed adults and retirees receive a small welfare payment from the treasury, and the president draws a salary.
Wages come out of the treasury, the president's salary too. Nearly all of it comes back: upkeep, medical bills, taxes, fines, share purchases, and the shop owners' property tax on what people spend in their shops. Food exports are the money that comes in from outside; luxury imports are bought only from what is left over, so a silo can only afford the comforts it earns.
Short pay: when the treasury can't cover the day's wages, everyone is paid the same share of their wage. The log says so on the first day ("💸 The treasury can't cover today's payroll: everyone was paid 55% of their wage."), every 30 days while it lasts, and when wages are paid in full again. Each short day stirs unrest in step with the cut, and a long spell brings strikes.
A rainy-day reserve: the treasury keeps three months of wages before it spends on extras: luxury imports, automation tools, buying into a neighbour's fund, dividends and recruiting bonuses. Emergency food and medicine are bought whatever the reserve.
A new silo starts with $150,000 in its treasury (about what a running silo holds).
Hunger: on full rations everyone's hunger settles back toward "fed" each day; only real shortages (partial or no rations) push people toward starvation.
Cost of living: every day each adult pays $3 upkeep (quarters, power, rations) and parents pay $1.50 per child. Each day a doctor treats you costs $4, and chronic check-ups a little. Costs come before any shop spending; a partner covers what the other can't; nobody is refused care, and what nobody can pay is written off. The money goes to the treasury, which pays welfare. Low-paid workers with children, the unemployed, the long-sick and heavily taxed households are the ones who fall into poverty -- about 3-10% of people 14+ in a healthy silo. (Jail already takes all of a prisoner's savings.)
Taxes: Bureaucrat and Industrialist presidents tax wages (the tax goes back into the treasury the wages came from).
Shops: eight shops, each run by one owner chosen by reputation. People's spending on comforts becomes the owners' income, and owners pay a property tax on their wealth. People go where they need to (the hungry for a meal, the unhappy for a drink, the single for tea), and each visit does something:
Spirit Shop: lifts the mood, but drinkers start more fights that day. About one visit in 30 ends with someone having a little too much (twice as likely for the unhappy, and twice again for someone who also drank the day before; never a pregnant woman). The morning after, they work at three-quarters of their usual output. A man who has had too much gets into a fight that night about one time in 33, a woman half as often. The other one is another of the day's drinkers if there is one, and usually a man (men mostly fight men). Both lose some happiness and one comes off bruised. With assaults and breaking points, about 5–6% of men and 3–4% of women are in a fight in a year (real surveys: about 5% and 3%). If the guards step in, the drunk one is fined $40 to the treasury, with no jail and no record. About one fight in 20 turns serious and is dealt with as an assault. Every drink takes sugar from the farm's cane; with none, the shop shuts (see Crops & sugar).
Burger Bar: takes the edge off hunger.
Furnishings: a comfier home, so better sleep for a month.
Book Shop: nudges the colony's education up.
Clothing Shop: warm clothes, so fewer colds and flu for a season.
Steam & Shears (bathhouse & barber): fewer stomach bugs for two weeks and a small boost to reputation.
Tea House: helps singles pair up and cools unrest.
Rust & Rivet (salvage & repair): turns scrap into a trickle of Components; stolen goods turning up here helps catch burglars and parts thieves.

Shops can be reassigned, closed, reopened and renamed from the editors (a renamed shop keeps its effect). Older saves gain the three new shops automatically.

People don't shop every day: each day a person has a chance of going out (about 60% for the wealthy, 40% for the middle class, 25% for those just above their savings reserve), and a trip spends a few days' budget. Crises (food or water shortage, outbreaks, hurricanes, grief) keep people home, and a daily swing means no two days look alike. Every visit is a purchase. The activity log gets one shopping line a day (visits, money spent, busiest shop) plus a couple of named purchases for flavor, such as someone buying a warm coat or meeting friends for tea.

The bank

Bankers (1 per 100 people, a skilled job, $14 a day) run the silo's bank. It lends the treasury's money, only from what is above the rainy-day reserve (three months of wages).
Who can borrow: anyone of working age under the $350 poverty line (cash and savings together), except the president and shop owners (the shop is their living), and not someone in jail, on the run, away on loan or still owing. Turned down, they wait 60 days before trying again.
The queue: each Banker at work gets through about two applications a day (a new one fewer). With no Banker at work the queue waits, and so it does when the treasury is down to its reserve; the log says so ("🏦 Nobody is at work at the bank: 3 loan applications waiting.").
Approval: someone in work with a reputation of at least 20, or someone out of work with at least 50. The loan is enough to get back to $500 ($50–1,000), with 10% interest on top.
Paying it back: a quarter of each day's wage goes to it before any spending. Nothing is taken from welfare.
Default: 60 days behind with nothing paid (days in jail don't count). The bank takes their cash and savings, then their shares in the silo fund. Whatever is still owed is worked off in 90 days of community service: someone out of work is put to sanitation or portering, whichever is shorter-handed, and their whole wage goes to the debt; what is left at the end is written off. About one in ten doesn't turn up (one in five with a short fuse or a jail record) and is jailed for debt evasion instead. After a default, no new loan for a year.
Debts end when the borrower dies or flees a disaster: they are written off. Nobody moves away owing the bank, and a partner who owes holds the family here too, as a work contract does.
A Corrupt president now and then has the bank lend a friend $2,000–5,000 that is never repaid, and pockets 40% of it as graft.
Savings accounts: once a month, someone with cash above $500 may put 30% of what is over into savings, at 2% a year, paid by the treasury. Cautious people do it more often (the gloomy, those 50 or older, anyone burned in a fund crash in the past year); optimists less, keeping to the silo fund. Shop owners save too. Anyone whose cash falls under $200 takes enough out to get back to $500. When someone dies or leaves, their account is paid out to their estate or with them. Jail takes savings along with cash. The shop owners' property tax counts their savings.
What the bank does with savings: it keeps a fifth in the vault and lends the rest to the treasury when the treasury can't cover the day's wages, instead of everyone's pay being cut. The treasury pays it back from what it holds above three months of wages, and nothing is spent on extras until it has.
Bank runs: high unrest, a global market crash or a Banker caught stealing sends 30-60% of the savers (the most frightened first) to take everything out — no more than once in 180 days. If the bank can't pay them all, even with the treasury paying back everything it has, it freezes withdrawals for 30 days, and unrest rises. So it does if the treasury can't pay back what a saver needs.
Savings are not guaranteed: when the bank reopens, the council pays back what it can; whatever it still owes is lost, and every saver loses the same share ("🏦 The bank has reopened. The council could not pay back what it borrowed, and every saver has lost 34% of their savings."). Someone who dies or leaves while the bank can't pay in full gets the same share.
Where it shows: the log; the lookup tool's Loan and Savings lines on a sim, and the Bank line on a silo's status (loans, savings, the vault, what the treasury owes, any freeze).

Robots

Stair-Crawlers, the Hazmat Scrubber, Surface Walkers and Mentor Walkers.

Clunky, spark-spitting tread machines that haul goods up and down the central stair. The administration uses them; the people hate them -- a machine eating parts and power while people go short.

Founder relics: once, a silo searches its lower stores (a new silo on its first day, an older one on the first day after this was added): 3 in 10 silos find none, 4 in 10 one and 3 in 10 two. Relics are built to last: they break down about once a year, and only 3 in 100 breakdowns finish one. Nobody can make another.
Scrap-built: the administration orders one from the machine shop when the porters have been short-handed 30 days running, or a machine has been lost -- but not within 60 days of a riot, only if the treasury still keeps a month of wages (and anything it owes the bank) after the $3,000 it costs -- a machine is essential, so it needn't wait for the full three-month rainy-day reserve -- and only if the 150 parts it takes leave 20 days of parts for the seals, the air and any Crawlers. The Machinists weld it over 30 days (4 at the bench; slower with fewer, stopped with none). A scrap Crawler breaks down about three times a year, and 15 in 100 breakdowns finish it. Each is named in turn: Crawler-1, Crawler-2...
At most 2 per silo, working or being built.
Work: each Crawler hauls what 4 Porters do, so the stairs need 4 fewer Porter posts (never fewer than one -- someone loads it). The day a new one starts, any Porters over the posts are moved to the open posts the job board most needs filled, keeping their wage; only if there is no open post anywhere are they laid off (the least practised first; not someone on community service). While one is broken down or dark the administration doesn't hire Porters back -- the stairs just carry less.
Upkeep: a relic eats 1 part a day and a scrap Crawler 1.5, but never the last day's worth the seals and air need. Without parts it wears down, breaks down more often, and at the end seizes up. The machine shop counts the Crawlers' parts when it decides how many Machinists it needs.
Power: charging, each draws what 8 people do. With the reactor throttled (the president's choice when the silo overheats) or down, they stand dark: no hauling, no parts, no power.
Breakdowns: one seizing up blocks the stairs for the morning (15% less carried that day). A Machinist at work mends it with 20 parts, usually within a few days. A breakdown that finishes one leaves a wreck the Machinists strip for 20-40 parts.
Resentment: machines only stir unrest while people are out of work. With 10% or more of working-age adults jobless, unrest grows 10% faster for each Crawler at work; with fewer jobless, less (5% jobless, half that); with everyone working, not at all. People get used to a machine over its first year at work, down to half the resentment (a Founder relic has always been there). A new one rolling out of the shop raises unrest a little. A Porter moved to another post for one minds little. One laid off (no open post anywhere) is 15 points unhappier, raises unrest a little, and carries it for 180 days ("lost their job to a machine", a breaking point strain).
Goodwill: when people see a machine save them, unrest eases a little (2 points): a Scrubber going into a toxic backlog or the reactor hall so the crews needn't, a Walker out in a storm or fire so fewer Ranchers are, a machine taking on the worst of a surface clean-up. "🤝 ... -- people grumble less about the machines."
Riots: rioters hunt the machines down -- each Crawler is caught half the time (more with too few Guards). A scrap Crawler caught is smashed to scrap; a Founder relic is usually only beaten and wrecked inside (60 parts to mend), and destroyed one time in four.
In the log: "🤖 The Machinists have got Crawler-1 running again -- a Founder relic found under tarps in the lower stores...", "🤖 With Crawler-2 at work, the administration has moved 2 Porters to other posts: ... Nobody loses their wage.", "💢 Crawler-1 broke down on the stairs, spitting sparks...", "⚙️ With the reactor throttled, Crawler-1 stands dark on the stairs...", and the riot line says what the crowd did to them.
The Hazmat Scrubber: a squat, sealed machine on tracks, built to go where people can't. One per silo, on top of the Crawlers. It takes nobody's job: it sits in its bay (half a part a day, never the seals' last day; without parts its seals perish and it seizes up) until it is needed.
Founder relic: once, a silo searches for one; 1 in 4 has it.
Toxic waste: when a backlog turns toxic it rolls into the waste works and clears up to 48 a day (4 Engineers' worth) while the crews stay out. If that isn't enough, the crews go in to help it, at half the exposure (see Waste management). It needs charging: with the reactor throttled or down it can't go in. A day in the waste works is hard on it (five times the breakdown chance).
Meltdowns: it goes into the reactor hall on its own charge, where nobody can work safely: the repair, and the decontamination of the reservoir, take a third less time. Then it may seize up in the hot zone and stay there for good -- a relic 1 time in 10, a scrap one 1 in 3.
Scrap-built: ordered when crews were hurt clearing a backlog with no machine to send in, after a meltdown with none, or when the last one was lost -- $4,000 and 200 parts, on the same money, parts and riot rules as a Crawler. The machine shop builds one machine at a time and takes whichever wanted machine it can afford: a Scrubber first, then a Crawler, then a Walker. Short of the money or parts for a Scrubber, it builds the cheaper machine meanwhile. The shop has one chance a day (1 in 20) to take an order, however many machines are wanted.
Riots and repairs treat it as they treat a Crawler.
Surface Walkers: tall, stiff-legged machines for the rough ground up top, at most 2 per silo. Founder relics (each silo searches once: 3 in 10 find none, 4 in 10 one, 3 in 10 two) or scrap-built ($3,000 and 150 parts, ordered after people are hurt on the surface with no Walker out there, or when one is lost). Parts, power, breakdowns, repairs, riots and resentment as for a Crawler.
Work: each tends what 2 Ranchers do, so there are 2 fewer Rancher posts per Walker (never under one); surplus Ranchers move to other open posts the day a new one starts, or are laid off if there are none ("lost their job to a machine").
Storms and fires: when a tornado, hurricane or wildfire hits, each Walker at work keeps 2 people inside who would otherwise be out in it -- but 3 times in 10 a Walker out there is knocked down (and now and then wrecked for good).
Clearing up after a tornado or a hurricane: the same day, one machine goes up to help, if it can be charged: the Scrubber (unless it's busy in a toxic backlog) halves the days left; otherwise a Walker, or failing that a Crawler taken off the stairs (its hauling stops while it's up there), takes a third off. It stays up until the clean-up is over, or it breaks down or loses its power. The machine shop's order of need: a Scrubber first, then a Crawler, then a Walker.
Where it shows: the lookup tool's A robots (each machine, its state and condition, any being built, what they have cost and done, who was laid off for them, and how many people went into toxic backlogs themselves), the Robots line on a silo's status, the Robots card on the dashboard, and the 3D view: Crawlers keep the porters' hours, hauling crates up and down the stair and across the floors, and charge at posts beside the Scrubber's bay, at the front of the Workshops floor, the rest of the day; one broken down stops where it is, red lamp and smoke; with no power it stands still, lamp off. The Scrubber waits in its striped bay at the front of the Workshops floor (green lamp, red when broken), is out by the fouled pond on a toxic-duty day, and sweeps the surface while it clears up after a storm. The Walkers work the surface in working hours, and are out with the crew whenever a storm or a fire comes (at night they come down to the server room to charge, in two cradles at the front left of the floor). A Crawler sent up to help clears the wreckage up top. Click one to see what it is doing.
Mentor Walkers: two short indoor walkers per silo, slate blue, with a lit screen for a face and an open manual. Every silo got its two the first day they came (a one-off delivery; they are never rebuilt, and are mended rather than wrecked). Each carries the manuals for a set of trades: Mentor-1 for Pharmacist and Structural Engineer, Mentor-2 for Banker, IT Operator and Archivist.
Teaching: while a trade's know-how is lost, its Mentor teaches the newcomers in it as fast as a teacher lent by a neighbour (a beginner masters it in about 100 days instead of 584 alone). The know-how stays lost until a person masters it.
Standing in: while nobody is at work in one of its trades, the Mentor does the work at half a person's output (the medicine, the seals, the bank counter, the network, the records office) until someone is hired.
They eat half a part a day, break down and are mended by the Machinists, and rioters may smash them up. They take nobody's job, so nobody resents them, and they charge from the battery bank, so they draw nothing the reactor would notice; with the reactor down or throttled they stand dark.
The log says when one starts standing in or teaching. The lookup, the dashboard's Robots card and the 3D view show them: Mentor-1 by the clinic and Mentor-2 by the records office, on the Commons.

Holidays & festivals

Four yearly festivals give each silo's year a rhythm (each silo keeps its own calendar):

Founding Day (2 days) on each anniversary of the silo's founding. Silos are founded on the first day of spring, so when the thaw comes within 10 days of it, the two are celebrated together.
Midwinter (1 day) halfway through each winter.
Festival of Lights (3 days) when a winter turns into The Long Dark: Winter Grey spells are half as likely during it and for two weeks after.
Thaw Festival (2 days) the day spring comes, when that's not close to Founding Day. The first thaw after The Long Dark is the biggest.

While one runs, shops are about 60% busier (the Spirit Shop and Burger Bar most of all), everyone gets a small daily happiness boost, and there's a little more petty crime and drunken trouble. A festival due during a real crisis (an outbreak, meltdown, seal emergency, food or water crisis, or hurricane) is cancelled instead, with a small disappointment. Festivals and cancellations appear in the activity log, the newsletter and the dashboard's Recent Events; the lookup tool's silo status shows the one under way (or the last one), and the mesh map marks a silo celebrating with 🎉.

Weather & the wild ecosystem

Weather: sunny, cloudy, rainy, stormy, windy or foggy, following realistic patterns and affecting crops, mood, crime and disaster odds.
Seasons: spring, summer, fall and winter shift the weather and are visible as seasonal colors in both views.
Winters vary in length: a normal winter is about 92 days, but each year's can come early (cutting fall short) and run late into the new year (delaying spring). About 1 year in 8 is a mild winter (60–72 days) and about 1 in 8 is The Long Dark (115–130 days). The log and newsletter announce winter's arrival (early, late or on time), "The Long Dark has set in" once a long winter passes 95 days, and how many days it lasted when spring comes. The snowpack and spring thaw follow the real winter. Each silo has its own run of winters, stored in its save as a season seed, so the same year can be hard in one silo and mild in another. Screens show "Winter (day 40)" and add "The Long Dark" when it applies.
A full food web: grass feeds rabbits and hamsters, which are hunted by foxes and eagles; bees and ants help crops and are hunted by raccoons and spiders; fish live in the pond.
Wildlife affects the colony:
Crop raids — crowded or hungry rabbits and hamsters eat the crops. Farmers and predators keep this in check.
Trapping drives — when raids drag on, Farmers cull the grazers and the catch becomes food.
Fox raids — hungry foxes break into the pens and take chickens and rabbits; Ranchers protect them.
Ants and spiders — summer ants spoil surplus stored food; spiders keep ants down and reduce pest outbreaks.
The grass always grows back: grazing never takes the last 200 units (roots and seed). Without that floor a surface stripped bare — after an eruption, say — stayed dead for ever.
Livestock: cows, pigs, sheep, horses, chickens and hutch rabbits, tended by Ranchers, produce milk, meat, wool and eggs.

Disasters

Tornadoes — strike the surface with no warning. Only the Ranchers and Firefighters working up top can be hurt or killed; everyone inside is safe, though the silo shakes and the seals take strain. Livestock and some food are lost. Wreckage is left strewn across the surface for 6-12 days: the Ranchers spend half their days clearing it, so the animals get half the tending until it is gone (a machine sent up shortens it -- see Robots).
Wildfires — burn the surface: the wild grass and animals, livestock in the paddocks, and the Ranchers and Firefighters working up there. Smoke drawn into the air intakes fouls the air for a while. Most likely in dry spring and summer weather, and never in winter. Firefighters limit them.
Interior fires — rarer, but inside the sealed silo. They're likelier when the power is failing and in winter, and vandals sometimes set them (arson). Where a fire starts decides what burns: food in a storeroom, Components in the workshops, a crop in a farm bay, families' belongings in the living quarters. Smoke is the main danger, and Firefighters decide how far a fire gets. A kitchen fire behind the Burger Bar, or an arsonist setting fire to a shop front, closes that shop for repairs: 1–2 days for a small fire, 3–6 for a bigger one, 1–2 weeks if it burned for hours. The owner keeps the shop but has no customers and pays for the repairs; the log and the shops page say when it reopens. To test it: edit-colony --trigger-shop-fire (a random open shop) or --trigger-shop-fire "Tea House" in the CLI editor, or the GUI editor's "Trigger Shop Fire" button.
Hurricanes — arrive with a few days' warning, make landfall, then need weeks of recovery. The warning gets most surface workers inside, so only a few Ranchers and Firefighters caught securing the herds are at risk; Engineers' preparation cuts that further. The seals take strain. A machine sent up after landfall shortens the recovery (see Robots).
Volcano eruptions — each landmass (Western Shelf, Central Ridge, Eastern Shelf) has one volcano, and an eruption belongs to the whole landmass: the silo where it starts publishes it and every other silo there follows, a day behind at most. About once in 28 years per landmass. Nobody is killed by the eruption itself — everyone is below and the hatch is shut. It runs in four stages:
Rumbling (5–15 days) — a warning in the log; nothing else yet.
Erupting (2–4 days) and ash fall (7–14 days) — ash clogs the air intakes. The air filters use three times the usual Components for as long as ash is in the air, the best the scrubbers can manage is 75% of normal while it is coming down, and the Machinists work overtime (30% more parts). On the day it erupts half the wild grass and bees and a fifth to a third of the wild animals are lost. When the ash starts to fall there is a 1 in 4 chance it gets into the reservoir (the same contamination a meltdown can cause).
Ash dark (30–60 days) — the ash hangs in the sky and hides the sun, a Long Dark out of season. Winter Grey behaves as in the worst of a Long Dark and new cases come 15 times as fast; the bees stop helping the crops; the wild surface lives as it does in winter. The Festival of Lights is held when it sets in.
One to three silos lose their transit link. On the day it erupts a local quake (the size of an aftershock) shakes the chosen silos and brings down the tunnel: no people, goods, crews, teachers or stock trades in or out until the Structural Engineers dig it out — 5 days fully staffed, up to 14 with none. Neighbours still hear from a cut silo and wait: anything already in the mail arrives when the link reopens, and people on loan stay where they are until then.
Reactor meltdowns — kill and injure people and knock out power until Engineers repair the reactor. Radiation contaminates 15–30% of the stored food, the farms fall back to emergency power (about a third of normal output, with no automation), and the cold stores fail so food spoils faster. A meltdown can drain weeks of food.
Pest infestations — destroy 20–40% of stored food and cut harvests for weeks. Good farm staffing makes them less likely, but only softens the damage a little.
Grief and fear: after a deadly meltdown or hurricane the whole colony is shaken, the families of the dead most of all. Mood takes weeks to recover, and more people decide to leave for a few months.
Every disaster can be triggered from the editors.

Presidency

Elections every 4 years, weighted by reputation. Each president has one trait with a real effect — helpful ones (Industrialist, Workaholic, Encouraging, Immigration Champion, Scientist) and harmful ones (Corrupt, Bureaucrat, Isolationist, Populist, Negligent). The presidency is a full-time job.
Censorship: when a crisis appears, the administration chooses to announce it (more unrest, but a faster response) or suppress it (calm, but a slower recovery).
With the network down (see IT Operators, under Jobs & the economy) there is no keeping anything quiet. A crisis that starts then is always announced, whatever the president would have chosen ("📣 With the network down the administration could not keep it quiet: ..."), with an announcement's usual effects. And the crises already hidden are as exposed as with an empty records office: 8% a day each, however well the office is staffed.
Leaks: a suppressed crisis stays secret only as well as the records office is staffed. For the 14 days it is fresh it can leak on any day after the first (but not on a day the administration is deciding about another crisis): an 8% chance a day with no archivists, falling in step with the office's strength to nothing when every post is filled by an experienced archivist at work. A beginner counts for 70% of an experienced one; an archivist on strike, in jail or home sick counts for nothing. With the office empty a hidden crisis leaks about two times in three.
What a leak costs: one and a half times the unrest an announcement would have caused, none of the faster response (the slow recovery stays), and 10 points off the reputation of the president who hid it (a successor is not blamed for a secret they inherited). The log says "🗞️ It has leaked that the administration hid the state of the food reserves -- the records office was short-handed." (or "-- with the network down nothing could be kept in."). The newsletter then reports the crisis in full, as a leak, and stops withholding facts about it.
Colony newsletter (every 30 days, looking back 30): opens with a "Colony at a Glance" summary and the news. Announced crises are reported in full, and so are leaked ones; suppressed ones only as vague rumors. With a local LLM it adds a written lead story and news section; without one it still works as a plain list. Coworker friendships and feuds are folded into one line.
Written ahead: the dashboard writes each issue as soon as it falls due, whether or not anyone has the page open, so a finished issue is waiting. While the next one is being written, the page shows the last finished issue with a note that the new one is at press, and swaps it in when it's ready.
The facts desk: below the news, plain facts taken by code (never the LLM) from the colony's records, each with its source — The Ledger (population, food, water, treasury, morale, poverty), Economy & the Exchange, Health, Crime & Courts, Works & Life Support, Work, the Mesh Desk (aid sent and received, allies and rivals, neighbours in trouble) and Weather & Season — then Community Notices and one resident's life story.
What gets cut: fixed rules decide which unwelcome facts are withheld. A Corrupt administration hides bad news about the treasury, poverty, crime and the silo fund; a Negligent one hides it about infrastructure, sickness, deaths and staffing; any administration hides the subject of a crisis it chose not to announce. A withheld fact is printed as a soft official line with no source, and the LLM is only ever given the published version. The page says how many facts were withheld, and "Show what was cut" reveals the record and its source. This is display-only: it doesn't change the simulation.
The News section is cut by the same rules. Before, an issue could print "Order is being kept throughout the silo" under a report of a theft nobody was caught for. Now a news item is left out of the printed edition (and never shown to the LLM) when it is bad news on a subject the administration is hiding. Good news on the same subject still runs: a Corrupt administration prints the arrest and the recapture, not the escape; a Negligent one prints "the waste backlog has been cleared", not that it reached critical levels. The administration's own "quietly decided not to disclose…" line is never printed. Rumours and news of who gets on with whom are residents' talk and are never cut; Community Notices (births, marriages, deaths) are left alone. Cut items are counted on the page and revealed by "Show what was cut". Across three snapshots (63 issues) this changed 8 issues and cut 14 items; the other 55 are word for word the same.
Impeachment: severe, sustained unrest can remove the president and force a snap election.
Corruption comes out: a Corrupt president's skimmed export money is tracked. While they're in office it can be exposed any day (about a 70% chance over a term) — a scandal, 60% of the graft seized back for the treasury, and impeachment on the spot. After they leave office the chance fades over a few years.
Disgraced ex-presidents (impeached, or exposed for corruption):
their reputation is held at 20 or below for 5 years, so shop and election odds are a tenth of normal and they can't be a Doctor, Guard or Teacher; they're unhappier, fading over the same 5 years;
up to 5 of the people who struck in the four months before (for corruption: the poor and the Farmers whose harvests they skimmed) become bitter rivals. These grudges flare up anywhere, not just at a shared job, send both home for the day, and heal far more slowly;
once a month they may spend 40% of their savings to flee into exile in a neighbouring silo, with their family. The silo they fled thinks less of the one that took them in, the new home resents the silo that let them go, and their coworkers and family there are a little gloomier;
when a pump breaks, pests hit the farms, a seal leaks, an outbreak or toxic spill starts or the reactor melts down, there's an even chance the rumour mill (the local LLM, or built-in lines) blames them, and their name takes another hit. The lookup tool shows "⚖️ Disgraced former President of Silo X", and any graft — including skimming nobody has found out about yet.

Global markets & trade

Food trade: the colony sells surplus food (never food it needs) and imports food when running low. Imports take 3 days to arrive, each day's order is limited to 40% of the colony's daily food need, and prices climb (up to triple) the more the colony keeps buying — money can soften a shortage but not make it vanish.
Food doesn't keep forever: stored food spoils a little each day (faster in summer or during a power outage), and the stores hold at most 120 days' worth.
Market crashes: rare price collapses. Export jobs (Farmers, Ranchers, Fishers) lay off some workers until prices recover.
President effects: an Isolationist blocks trade except for emergency food and medicine; a Corrupt president pockets a share of export income.
Spending a surplus: a wealthy colony buys automation tools and luxury imports that lift everyone's mood, from what it holds above three months of wages.

Stock market

Every silo has a fund with a share price (starting at 100) that changes once a day. It drifts toward a fair value built from how the silo is doing — food, water and parts in days, seals, happiness, unrest, Silo Syndrome, the past year's population growth, treasury per person, and any outbreak, reactor trouble, seal emergency or market crash — with day-to-day noise on top.
News moves it: a meltdown (−20%), impeachment or corruption scandal (−10%), outbreak (−8%), earthquake, riot or sabotage (−5%), strike, seal leak, pests or a broken pump (−2 to −3%), a global market crash (−15 to −25%, every fund at once), a festival (+2%).
Residents invest: about half the adults with savings do (80% of the wealthy, 50% of the middle class, nudged by temperament; reconsidered once a year). Each month an investor tops up or trims toward 30% of what they own above a $500 cushion — investing never takes their cash below $500. The money goes into the treasury; selling is paid from it. Anyone whose cash falls under $200 sells shares to get back to $500. The fund pays a 1% quarterly dividend when the silo is doing well.
Crashes hurt: a 20% fall in a month sets off panic selling (about 30% of holders sell out and stay out for six months; unrest ticks up), and anyone whose holding of $200+ lost a quarter or more in a month takes a happiness hit.
Councils invest in each other: once a month a council may put 10% of its treasury (above the reserve of three months of wages) into the neighbour that's the best mix of good value and good relations — never one it's cool or hostile toward. The money really goes into that neighbour's treasury; dividends and sale proceeds come back the same way. Stakes stay under 20% of the buyer's treasury, a single purchase under a quarter of the target's, and a stake under half of it. Investing warms relations a little both ways; a council dumps its whole stake in a silo it turns hostile toward (a −5% sell-off there, and resentment), and takes half its profit on a fund priced 40% over its fair value.
Crowded funds and limited withdrawals: money other silos invest is spent like any other treasury money, so a popular fund can come to owe more than the silo holds. To keep that in check — without making it impossible:
a fund's fair value only counts the silo's own money, not what others have invested;
councils won't buy into a fund once other silos hold half its treasury, and holders of a fund that owes more than its whole treasury pull out a fifth of their stake each month;
a fund pays out at most 15% of its treasury a month to departing silos, and never dips below its reserve. What it can't pay stays as shares (nothing is cancelled unpaid); the log reports "withdrawals limited", the price drops 3%, and the sellers think less of that silo. The ticker marks a fund that owes more than its treasury.
Wealth classes count shares as well as cash ("wealthy" is $5,000+ in all); poverty still goes by cash in hand. Shares are sold when someone moves to another silo, go into the estate when they die, and are forfeited when they're jailed.
The ticker (/ticker, button on the dashboard): a scrolling tape, the population-weighted Mesh Index, every fund's price, day and 30-day change, a 90-day trend line, fair value, shareholders, what residents and other silos hold, its stakes elsewhere, and the latest news; click a silo for its last year. The tape also runs under the scene on the dashboard and across the top of the monitor page (/ticker?strip=1); click it to open the full page.

Healthcare, epidemics & outbreaks

Everyday illness: sims catch colds, stomach bugs and flu, which can turn into pneumonia.

| Illness | Lasts | While sick | Notes | |---|---|---|---| | Cold | 4–8 days | works slower | common, especially in winter | | Stomach bug | 2–5 days | mostly off work | worse when water is contaminated | | Flu | 7–14 days | off work | autumn and winter waves | | Pneumonia | 10–21 days | off work | the dangerous one |

Illness spreads within families, between coworkers and among children, more in winter and in bad air. Babies, young children, the elderly and the frail are hit hardest.

Doctors each see about 6 patients a day, most urgent first. Treated patients recover faster and rarely get pneumonia.
Chronic conditions — lifelong, and they run in families:

| Condition | What it does | |---|---| | Asthma | asthma attacks, worse in bad air or with a cold | | Heart condition | develops with age; heart attacks can be fatal | | Weak immunity | catches everything more easily and gets sicker |

Doctors give monthly check-ups; when they fall behind, attacks become more likely.

Silo Syndrome — the two psychological conditions of a life spent underground. Unlike the physical ones, people can recover from them.

| Condition | What brings it on | During a spell | |---|---|---| | Winter Grey | fall and winter (worst in The Long Dark), grey weather, unhappiness | works at 65%, a 1-in-4 chance each day of not facing work at all, sleeps badly | | Wall Fever | seal emergencies, high unrest, winter, unhappiness | works at 85%, picks fights with coworkers (sometimes starting a rivalry), much likelier to join a strike |

About 5–10% of adults have one. Most days they're fine; bad stretches bring on a spell of a few days to two weeks, with a small daily drop in happiness.

Winter Grey keeps to the dark half of the year. Someone who has it carries it all year, but a spell can only start, and a new case can only be diagnosed, in fall or winter — or under volcanic ash, which hides the sun whatever the calendar says. In spring and summer they are simply well. A spell still running when spring comes runs its course. The chance of getting it in a year is what it always was, with all of it now falling in those two seasons; a spell is three times as likely on a winter day as on a fall one. Wall Fever can strike in any season.

What helps: Doctors (check-ups make spells rarer, and visits during a spell shorten it), a partner, belonging to a club, shop visits (a trip out shortens a spell, and a recent treat makes one less likely) and, for Winter Grey, sunny days, especially for Ranchers, Fishers and Firefighters working up top. It runs in families, and a diagnosis or recovery goes into the sim's life story. See it with A syndrome in the lookup tool, on the dashboard's Chronic line, and in the editors (it can be added or removed like any condition).

Medicine: Pharmacists make medicine, which doctors use to treat the sick and manage chronic conditions. Without it, treatment is much less effective. The colony buys medicine when supplies run low and can trade it with other silos.
Outbreaks are named diseases that spread from person to person:

| Disease | Caused by | Notes | |---|---|---| | New strain of flu | bad weather, seal leaks | nobody is immune | | Measles | bad weather, sick arrivals | spreads fast among children | | Dysentery | toxic waste backlog | spreads through dirty water and food |

A Scientist president makes outbreaks milder; a Negligent one makes them worse. A sick migrant can carry an outbreak to another silo.

Triggers: outbreaks (with a choice of disease), illness waves such as a "flu season", and medicine stock can all be set from the editors, even while the simulation is running.

Grief, funerals & crisis

Grief — when someone dies, their partner, parents, children and brothers and sisters (from the age of 5) grieve. Their happiness drops on the day, and the level their life settles at stays lower for 90 days, fading as the weeks pass. Losing a partner or a child weighs most, then a brother or sister (half-brothers and half-sisters count), then a parent. A death by suicide weighs more again.
Funerals — the day after a death the family holds a funeral in the Commons. The spouse or partner holds it; if there is none, the living parents; if there are none, the grown children. With none of those there is no funeral.
The family (partner, parents, children, brothers and sisters) take the day off work for it. Friends from work and the dead person's club come when their shift is done.
The hosts pay the council's fee of $60 between them, or as much of it as they have.
The family who were there grieve for a shorter time: the funeral lifts 30% of the grief still to come.
The service follows the tradition of the dead person's religion, and it goes into the hosts' life stories and the newsletter's notices.
When four or more people die on one day (a disaster), the silo holds one memorial for all of them in place of a funeral each.
Crisis — the weeks in which someone may take their own life. It is rare, for adults only, and never comes from one thing: troubles have to pile up.

| Trouble | Weight | |---|---| | Grieving for a partner or child | 1.2 at first, 0.6 by the end | | Very low happiness for six weeks or more | 1.1 | | In disgrace | 1.0 at first, fading over the years | | Lives with Winter Grey | 0.9, and 0.5 more during a spell | | Of working age, out of work and poor | 0.7 | | Alone: no partner, no club, no close friend | 0.7 | | Three months or more still to serve in jail | 0.6 | | A chronic illness while the doctors are behind on check-ups | 0.5 | | Born with a heavy heart (about one person in twelve) | 0.5 |

Only when at least two troubles add up to 1.3 or more is there any chance of a crisis starting, and the more they add up to the likelier it is. A partner, a club, a close friend, children at home and a recent festival each make it less likely.
A crisis lasts two to four weeks. The person works at half their usual rate and their happiness sinks further. The log says only that the people close to them are worried.
Every day their partner, family, a close friend, their club and a doctor with time to spare each have a chance of getting through to them. Most people are pulled through, and it goes into their life story. They are then safe from another crisis for a year.
On a day nobody gets through there is a 1 in 100 chance it is their last. About one crisis in ten ends that way: about one in twenty for someone with a partner, family, friends and a club, close to one in five for someone with nobody when the doctors are too busy.
A silo sees a crisis every year or two and loses someone this way about once in 10 to 20 years.
The death is recorded as suicide. The log and the newsletter say that the person took their own life, and never how. It is a family notice, which no administration can withhold. The family grieves, the funeral is held as for anyone else, and a bereaved partner or parent is at more risk themselves for a while.

Breaking points

The outward side of a crisis. A crisis (above) is someone turning in on themselves. A breaking point is someone who can't take any more and does something about it.
Strain: every adult's troubles are added up each day. Each one has a weight:
heavy — a spell of Wall Fever (1.0), disgrace (0.9, fading), very low spirits (0.8), a break-up or divorce in the last four months (0.7);
middling — poor, going hungry, out of work, just out of jail or on the run (0.6 each); grieving (up to 0.6, by how hard the loss hit, and a light grief does not count); living with Wall Fever, or unhappy, or laid off for a Stair-Crawler in the last 180 days (0.5);
lighter — a spell of Winter Grey, a recent bout of heavy drinking, sleeping badly, a short fuse, nobody close, being a refugee (0.4 each); struggling for money, an old jail record, night shifts, being ill, fresh bad blood with a neighbour, two weeks or more behind on a bank loan or on community service for one (0.3 each);
the whole silo — short of food or water (0.5), dangerously hot or crowded with refugees (0.4 each).
At breaking point: two or more strains adding up to 1.2 or more. One trouble alone, however heavy, is never enough.
Snapping: each day someone at breaking point has a small chance of snapping, higher the more they carry, and lower for each of a partner, children at home, a close friend, a club and a festival. At most one person snaps in a silo in a day, and nobody snaps twice within a year. It works out at about one a month in a silo of 200 that is doing well, and more in one that is not.
What they do fits who they are. About half do something undramatic:
walk off the job for a week or two (not someone on contract);
make a scene in the Commons, which raises unrest a little;
leave the silo for good, family and all (likelier for someone out of work or a refugee).

The rest do something that hurts:

sabotage their own post — an Engineer the reactor, an Atmosphere Technician the air scrubbers, a Structural Engineer the seals, a Water Technician the pumps, an IT Operator the servers, a Machinist or Porter the spare parts, a Pharmacist the medicine, a Farmer the food stores, a Sanitation Worker the waste works;
go for the airlock — only someone with Wall Fever, and most often in a spell of it;
attack the neighbour they have bad blood with (or, rarely, whoever is nearest) — a woman about a third as often as a man, making a scene instead;
spread a nasty rumour about the person they have bad blood with (or a neighbour, never their own family): a lie that costs them some reputation until it turns out untrue. Women do this far more often than men (research finds men lead in face-to-face violence, women as much or more in this kind of social aggression);
steal — a break-in, or food if they are hungry (likeliest for the poor, hungry and jobless);
set a fire (likelier for the angry: the disgraced, those just out of jail, the very low, the recently parted, those with a short fuse).

Nobody sabotages a post with nothing to wreck: a store that is empty, servers already down, a waste works already failing. And if there is nothing to steal or nobody to go for, they make a scene instead.

Consequences: the dramatic acts go through the ordinary crime rules. The Guards on duty may catch them, a guard may be bribed, and a sentence follows: 240 days for sabotage, a year for arson, the usual terms for the rest. Someone who goes for the airlock is exiled if caught and lost outside if not.
Who can't: the president, anyone in jail, on the run, away on loan, already in a crisis, or under 18. Nobody snaps in a silo's first year, when every founder is poor and short of everything. Nobody leaves without their family: not if the partner is held (the president, in jail, on contract, away on loan), and not if a child of theirs is in jail with no other parent here.
Afterwards: whoever has snapped has let it out. They do not go into a crisis in the year that follows. Taking one's own life is not one of the things a breaking point leads to; that belongs to the crisis rule alone.
Where to see it: the log names the person, the reasons and what they did ("⚡ … reached breaking point — poor, out of work and just out of jail — and set a fire."), followed by the report of the act itself, which says whether anyone was caught. On a silo with LLM narration the narrator adds one sentence about the moment. The lookup tool shows a Strain line on a sim ("AT BREAKING POINT" with the reasons), a Snapped line if they have, and a Breaking point line on the silo's status naming who is at breaking point now and what has happened so far. It goes in the sim's life story.

Crime

Crime comes from people: each resident 14+ has a small daily chance of offending, higher for young men, the poor, the jobless, the unhappy, the hungry and people with a record — and lower for those with a partner or children. The more likely people think they are to be caught, the less they offend.
What and when: why someone offends decides what they do. Most thefts and vandalism happen at night.
Need: food theft (a few days' food for their household, not the whole store), burglary of another resident's savings, shoplifting.
Access: medicine stolen from the pharmacy (likelier when medicine is short or a relative is sick), Components stolen from the workshops (which slows seal repairs), a shop owner skimming from customers and taxes. Insiders are harder to catch.
Anger: assault and vandalism; rarely, murder, likelier for someone with a record. An assault can turn fatal (manslaughter).
Despair: very rarely, someone tampers with the airlock to reach the surface. Caught in the act, they're exiled outside; otherwise they get out, damaging the seals and possibly causing a leak.
At the bank: a Banker may skim from the bank's books (embezzlement, 60 days if caught; the money is recovered); someone who doesn't turn up for community service is jailed for debt evasion (30 days). See The bank.
Bribery: a guard who has caught someone may take a bribe to let them go, far more often under a Corrupt president. Some bribes come out, and the guard goes to jail.
Guards: a day force and a night watch. More guards catch more offenders, with diminishing returns; a silo with no night watch solves almost nothing that happens overnight.
Jail: a caught offender loses their job and reputation and serves a sentence that fits the crime — a week for shoplifting, two months for assault, two years for manslaughter, five for murder — longer for repeat offenses. Stolen money and some stolen goods are recovered. A record keeps someone out of Doctor, Guard and Teacher jobs until their reputation recovers.
Fines: a minor crime costs a fine, paid from cash and then savings: $50 for shoplifting, $150 for petty theft or rioting, $200 for vandalism. Everything else they own stays theirs; what they can't pay becomes a debt at the bank, with the bank's 10% added once, paid from their wages like any loan (fall behind, and it's community service as for any loan). A serious crime (burglary, fraud, embezzlement, violence, arson, sabotage and the like) still forfeits all their cash, savings and fund shares.
Community service: for shoplifting, petty theft or vandalism, someone who is expecting a baby or has a child under 5 at home works off the same number of days in community service instead of going to jail. They keep their job but lose their spare time (a little less happy while it lasts, and they can't move away), and the fine still stands ("... was caught, fined $200 and sentenced to 20 days' community service instead of jail (small children at home)"). That holds for a first and second offence; a third means jail.
Escapes: prisoners can escape and become fugitives, and can be recaptured.
It's rare: about one prisoner in ten gets out over a sentence. The fewer guards on duty, the likelier it is; with every guard post filled, nobody does.
Most hide in their own silo. Only about one escapee in four gets through the airlock to another linked silo (one with breathable air that hasn't been abandoned).
What was left of the sentence goes with them, to whichever silo they reach. An escape does not wipe it out.
On recapture they go back to finish it. If less was left than the usual term for a recapture, they get that term instead.
A fugitive caught for a new crime serves the new sentence and what they still owed, one after the other.
Maximum security: nobody escapes twice. Anyone who has escaped once, from any silo, is held in maximum security from then on: for what is left of that sentence and for any sentence after it.
Killings on record: the silo keeps a permanent record of every murder and every fight that turned fatal: who died, who did it, when, and whether the guards caught them. The record names the killer even when the silo itself never found out.
Life inside: a prisoner sleeps in a cell (a somewhat worse night, but no baby or night shift keeping them up), misses festivals, club support, coworkers and home comforts, and is about 15 points less happy for as long as the sentence lasts. They can't start a relationship or have a baby while inside; an existing couple stays together, but a sentence doubles the chance they split up. The lookup tool shows "🔒 In jail, N days left (crime)" under the name.
Fugitives arrive without parent links (their parents are back in the silo they fled; their life story still names them).

Civil unrest, strikes, riots & sabotage

Unrest builds up from sustained hardship: food shortages, bad air, days of heat, a long market crash, widespread poverty, a silo over its head count or a sectarian feud more than a month old. Rare flashpoints can stir up even a healthy colony. Once the cause is gone it drains away at 3 points a day.
Strikes (unrest 30% and up): workers refuse shifts for a few days.
Riots (50% and up, an 8% chance a day):
A crowd gathers in the Commons, smashes shopfronts and fights the Guards. It is a tenth to a third of the people aged 16 to 59 who are free to join (never fewer than 10). The young, the poor, the unhappy, recent strikers, people with Wall Fever and members of a feuding religion are the likeliest to be in it.
About one rioter in five is hurt, and one Guard in four. About one in a hundred of those hurt dies of it.
The treasury pays for the damage: $50 to $150 a rioter.
The shopfronts they smash close for repairs: about one shop for every 10 rioters (at least one, more with too few Guards), each for 1 to 6 days. The owners pay for the repairs, as after a fire, and nobody can shop there until they reopen.
The crowd hunts down the Stair-Crawlers too (see Robots): scrap ones are smashed, Founder relics usually only beaten.
The Guards arrest up to 15% of the crowd. Rioting carries 30 days in jail, with a job and savings lost like any other sentence.
One Guard can hold three rioters. With too few Guards for the crowd there are more injuries, more damage (up to 1.6 times) and fewer arrests; with none, nobody is arrested.
Everyone who stayed out of it is frightened (3 points of happiness).
A riot lets off steam: unrest drops 25 points, and no second riot follows within 10 days. While the cause lasts, unrest climbs back.
Sabotage (60% and up): targets the air system, the treasury, the seals or the reactor.
Sectarian tension: every 10 days, two religions that each hold 15% of the adults have a 3% chance of falling out, twice that when the colony is on edge. No more than three feuds run at once. Each has a 12% chance every 10 days of ending in a reconciliation, never on the day it began. From its 30th day a feud raises unrest on its own, faster the longer it has run (at full rate from 180 days); it speeds up unrest from other causes by half; and it sways elections.
A single religion with a clear majority, and no feud, brings a little social harmony.

Waste management & life support

People and animals produce waste, which Sanitation Workers (and Ranchers, for the animals) process. If it backs up, it becomes toxic — hurting health and mood and risking a dysentery outbreak. Engineers help clear a backlog, and the pond turns murky in both views.
Going in is dangerous: the Engineers and Sanitation Workers at work who go into a toxic backlog each lose 5-15 health, and 1 in 20 comes out with pneumonia (half of both alongside a Hazmat Scrubber; nothing at all if the Scrubber clears it alone). Crews rotate: nobody is sent back in within 60 days. Their story says "Exposed clearing a toxic waste backlog".
Occasional processing breakdowns can cause a backlog even in a well-run colony.

Crops & sugar

The farm's beds are shared between four crops. Wheat, potatoes and beans all go into the one food store; sugarcane makes sugar.

Wheat is the steady staple. It keeps, so the more wheat is grown the less of the stored food spoils (a fifth less at the usual 40%).
Potatoes give about 30% more food per bed, and bad weather costs them half what it costs the other crops. But they can be hit by blight: about once in ten years for a silo on the usual mix, and four times as likely with twice the potatoes. For 30 to 60 days the potato beds give a fifth of their crop, which at the usual mix is a third of the silo's food.
Beans give about 30% less food per bed, but lift the yield of every other bed by up to 10%.
Sugarcane is barely food. It makes sugar, and it is thirsty: at the usual 10% of the beds it adds 3% to the silo's daily water use. The people come first: the cane is only watered while the tank is more than half full, and cane that goes short gives less sugar.
The usual mix is wheat 40%, potatoes 30%, beans 20%, sugarcane 10%. A silo on it grows the same food as a farm did before there were crops.
What gets planted: every 30 days the farm looks at what the silo needs and moves each crop by at most 10 points.
Food under 20 days: potatoes up to 50%, no sugarcane. That grows about 15% more food.
Water tank under 40%: sugarcane down to 5%.
Sugar under 30 days and food over 45 days: sugarcane up to 20%, which costs about 10% of the food.
Otherwise back towards the usual mix. Beans stay at 20%.
Sugar is kept in its own store, which holds 60 days of the Spirit Shop's usual pouring. Every silo starts with it full. Each drink uses one unit.
No sugar, no drink: when the sugar runs out the Spirit Shop shuts for at least a week. Its owner keeps it. It opens again once the week is up and there are three days of pouring in the store.
Between silos: a silo with more than 30 days of sugar sells some to the neighbour shortest of it (under 7 days, or with its Spirit Shop shut), at $2 a unit, as far as the buyer's treasury goes.

Water & drought

Water Technicians pump water every day, with extra on rainy and stormy days, into a reservoir that holds about 20 days of supply.
Winter: frozen ground slows pumping, and snow builds up as snowpack that refills the reservoir in the spring thaw. How much snow falls depends on the weather and the silo's size (its catchment), not its staff: a typical winter banks about a week of water, a heavy one more. The views show it as days of water ("Snowpack ≈ 9 days").
Drought: long dry spells cut output and evaporate stored water.
Pumps wear out and sometimes break and leak; Water Technicians repair them.
Contamination: a reactor meltdown can poison part of the water supply, forcing rationing until it's cleaned up.
Water shortages lower happiness and raise unrest.

Atmosphere & life support

Atmosphere Technicians keep the air clean. Poor air quality makes Doctors and Teachers less effective and lowers happiness.
Air filters use the same Components as seal repairs, so a shortage of Components hurts both.
Toxic air (below 30%) wears down health day by day — fastest for babies, the elderly and people with asthma, heart trouble or weak immunity. Deaths are recorded as "toxic gas exposure".
Machines on the air: with no Atmosphere Technician at work, the Hazmat Scrubber and the Surface Walkers run the air scrubbers (any not broken down, with the power on). The Scrubber gives 50%, each Walker 35%, and together at most 60%: enough to keep the air breathable, never as clean as a technician. The log says when they take over ("🤖 No Atmosphere Technician is at work -- Walker-1 is running the air scrubbers") and when they hand back. Before this, a silo that lost its technicians to toxic air could never get its air back: the poisoned were too sick to work.

Heat & cooling

A sealed silo can't easily get rid of the heat its reactor and machines make. Heat exchangers carry it away, and normally they keep up: the silo sits at 21°C (70°F).
What makes it warm (they add up when they overlap):
A heat exchanger breaks down: about once per silo every four years. 60% of the cooling is lost and the silo heads for 38°C (100°F).
A heat wave on the surface: about one summer in three, for 4 to 9 days. The heat has nowhere to go and the silo heads for 34°C (92°F).
Falling volcanic ash clogs the intakes: a small effect alone (27°C), worse with either of the others.
The rock is slow to warm and slow to cool: each day the temperature closes a quarter of the gap to where it is heading.
The repair: Atmosphere Technicians mend a broken heat exchanger, 6 to 12 days of work for a full crew. It uses Components every day; without parts the work goes at under a third of the pace. A short crew takes proportionally longer. A heat wave can only be waited out.
What heat does. Nothing up to 26°C (79°F); everything below at full strength from 38°C (100°F), in proportion between:
people drink up to 50% more water;
stored food spoils up to three times as fast;
the crops under the grow lights wilt, costing up to 25% of the farm output;
nobody sleeps well, and happiness settles up to 10 points lower;
heat stroke: the old (70 and over), babies under one and people with a heart condition can collapse, up to a 2% chance a day each at full heat. About one in seven of those who collapse dies; the rest are left weakened;
from the fifth day at 30°C (86°F) or more, tempers feed unrest.
The president's choice. Throttling the reactor cuts the heat by 40%, enough to hold the silo near 27°C with an exchanger down, but it halves the reactor's output, so power runs short for as long as it lasts, with everything that brings (see Jobs & the economy).
Most presidents throttle once it reaches 30°C. Encouraging, Scientist and Populist presidents throttle at 28°C; a Bureaucrat waits for 33°C and a Negligent one for 34°C.
Industrialist, Workaholic and Corrupt presidents refuse: output comes first, and the silo takes the full heat.
A throttled reactor can't charge the Stair-Crawlers: they stand dark and the stairs go back to the Porters alone.
The reactor goes back to full output once the cause is gone and the silo is down to 24°C.
A reactor that is offline makes little heat, so a meltdown's blackout is at least not a hot one.

Livestock & wild-animal economics

Fishing depletes the pond: fish sustainably and it holds steady, overfish and it crashes.
Livestock disease strikes cows, pigs and sheep from time to time; Ranchers limit the losses, and herds take a while to recover.
Dead animals are dropped from the save at the end of each day (the day's counts and events are already recorded). Before, every animal that ever lived was kept: Silo A carried 2,357 animal records for 296 living animals.

Air-lock structural integrity

Structural Engineers maintain the air-lock seals, which wear down from storms, earthquakes and traffic through the airlock. A family travelling together is one trip, and a day's airlock wear is capped, so a mass evacuation strains the seals without wrecking them.
Badly worn seals (below 30%) can leak. A leak drops air quality sharply and exposes the people near the breach: some die, others are hurt or get pneumonia, and asthma sufferers have attacks. A free doctor improves the odds. Leaks can also start an outbreak.
Seal emergency: declared when the seals fall below 30%, lifted once they're back above 60%. Repair crews work double shifts (faster repairs, worse sleep, lower mood), Machinists make more Components, and workers from less vital jobs (Teachers, Guards, Ranchers, Fishers, Firefighters) are put on repair duty at reduced skill. They go back to their own jobs when it's over. Neighbors put the silo first in line for Components.
Machinists make Components, the material needed for seal repairs. In a severe shortage, the colony may strip old infrastructure for parts — getting Components now at the cost of a permanently lower seal ceiling.
Parts shortage staffing: if the Components reserve stays under 10 days' worth for a week, the machine shop hires first and the council moves workers onto the lathes (about one every few days, from Guards, Teachers and other well-staffed jobs; essential jobs keep their floor, shop owners are left alone). It keeps going until the reserve is back to 20 days, and Machinists aren't moved off the lathes while the silo only has as many as it needs. Parts received from neighbours in the last 30 days don't count toward the reserve here, so a silo living on hand-outs still staffs its own machine shop.

Earthquakes

Strike without warning and aren't tied to the weather. They damage the seals, raise the risk of a reactor meltdown for a while, and can be followed by aftershocks. Structural Engineers reduce the damage.

Abandon and resettle

In a mesh, a silo down to fewer than 10 people is abandoned: everyone resettles, a household at a time, in the neighbour with the most room and breathable air (never turned away, even at a border sealed for fear of contagion: they have nowhere else to go) ("🏚️ Silo J has been abandoned. Its last 3 people have resettled in Silo T").
It stands sealed and empty for 60 days while its air is scrubbed. Then 60 settlers from outside reopen it ("🏗️ Silo J has been reopened: 60 settlers -- a full crew, every post filled --"), bringing what a new silo starts with (food, water, medicine, parts) and mending the seals first. Like founders, they stay their first year.
The settlers are a full crew, chosen for the silo's new size: someone in every job post (42 at 60 people), each skilled trade with an expert who knows it -- two each for Doctor, Atmosphere Technician and Water Technician -- and trained hands beside them, a keeper for every open shop, three retirees, and children for couples among them. Nobody starts out with a trade's know-how lost, and the quarrels of the old silo don't come with them (unrest starts at nothing).
A silo can also be refounded on purpose (the silo_refound.py tool): on its next day its people resettle with the neighbours as above, and a full crew moves in the same day ("🏗️ Silo J has been refounded. Its 45 people have resettled in Silo E and Silo I, and 60 settlers -- a full crew -- have come from outside").
The lookup's silo status shows an abandoned silo and when settlers are due, or when it was reopened.

Extinction safeguard

A manual reset that wipes out most people, animals and wildlife at once. It's only available from the editors and always asks for confirmation.

Cross-silo migration & trade

Several silos can run as separate programs and link up:

Pairwise mode links exactly two silos.
Mesh mode links any number through a shared folder; new silos are found automatically. The web dashboard's /mesh page shows every running silo and animated arrows for what's moving between them.

What moves between linked silos:

Nobody moves into poison: each silo's summary says when its air is toxic or it stands abandoned, and then nobody moves there, flees there, transfers there, is drawn there by lost know-how, escapes from jail to it or arrives from outside. (Before this, job seekers, outside immigrants and escaped prisoners kept walking into toxic air and dying.) The add-unemployed tool skips such a silo too.
Migrants: unemployed or unhappy people may move to a silo with job openings or happier people. Some are turned away. A new silo's founders stay put for its first year.
Know-how pull: someone who has mastered a skilled job and is thinking of moving tries first a neighbour that has lost the know-how for that job (if it has room), unless they're one of the last two at home who know it. Living in a crowded silo is reason enough for such an expert to go: they leave the crowding for the silo that needs them. The log says so ("..., which has lost its know-how as Doctors").
Skilled transfers: silos offer relocation bonuses for badly short jobs, and experienced workers may move from where their job is well staffed.
"Don't drain us": two rules stop neighbours' relocation bonuses from emptying a silo. People who leave on their own — unhappy, out of work, or fleeing a disaster — are never stopped.
The yearly allowance: neighbours may recruit away at most 5% of a silo's people in any 12 months, counting the partners and children who go with each recruit. A household only goes if all of it fits in what's left. When the allowance is used up the job board closes until the oldest of those departures is a year old.
The backstop: a silo more than 15% below its highest population of the last 3 years closes its board whatever the allowance says, and reopens once it's back within 10% of that peak.

Both the silo and any neighbour that's recruiting log when the board closes and reopens. The lookup's silo status shows the board and how much of the year's allowance is used; the health check reports people recruited away and days closed for each reason.

Families move together: anyone who leaves takes their partner and children. If the partner can't leave, nobody goes.
Records travel with them: each silo has its own day count and its own id numbers, so on arrival a newcomer's dates (life story, when the couple got together, illnesses and the immunity they left, a jail release) are turned into the new silo's days, and family links are renumbered. A baby on the way keeps its father if he came too; otherwise it is born with no father on record here. A shop owner arrives looking for ordinary work — the shop stayed behind.
Refugees: after a meltdown or hurricane, whole families may flee to a neighboring silo — especially those with young children, injuries, or a relative killed in the disaster.
Most of the silo stays. However many want to go, no more than a quarter of the people alive on the day of the disaster may leave over the whole crisis — and if a second disaster strikes before the silo is back on its feet, it is still that same quarter. The president, anyone in jail and fugitives never go.
Open borders. Each president who hears of the disaster decides, once, whether to open the borders to the stricken silo for 10 days. An Immigration Champion always does and an Isolationist never; anyone else does about one time in seven (15%) — half as often again for an ally, a quarter more for a friend, half as often for a cool neighbour, never for a hostile one. Nobody opens the borders while their own silo is short of food, water or medicine, fighting an outbreak, without power or dealing with a disaster of its own, nor to a silo with an outbreak or poisoned air (and if one starts there, the borders close to it again). A host that gets into such trouble itself while its borders are open closes them again. The log records the decision either way.
The exodus. The first day's wave goes as before, to one neighbour, with a quarter turned away at the door. On each of the next 10 days, while any neighbour's borders are open to it, more households leave (at three-tenths of the first day's chance, with the same things making a family likelier to go). They follow one another: all go to the same open silo, the one the stricken silo is on best terms with. A child on its own doesn't set off, and nobody leaves on a day the stricken silo has an outbreak or poisoned air. Nobody who set out on an invitation is turned away, however long the journey took, and nobody asks about places, so the host can end up over its head count (see Crowded with refugees, under People & life cycle).
A pledge of help. Opening the borders is also a promise: until the stricken silo is back on its feet — reactor running, no hurricane still being cleared up, not short of food, water or medicine — and for 60 days at most, it comes first for whatever the host has to spare. Food, water, medicine and spare parts go through the ordinary aid, never below what the host keeps for itself; "in need" is read half as generously again for it (under 15 days of food instead of 10, for example), relations don't hold the help back, and medicine and water are not charged for.
Goodwill. The stricken silo warms to every silo that opens its borders (as much as for a repair crew), and a little more for each family taken in; the host warms a little to the silo it helped.
Going home, or staying. Each family decides as it flees: about six in ten mean to go home, the rest to start over. Nobody goes home, or is counted as settled, in the first 90 days. After that a family that meant to stay is settled for good; one that means to go home does so on a day of its own choosing (about one chance in fifty a day) once home is back on its feet and the way is open — not while either silo has an outbreak or poisoned air, and not while one of them is president, runs a shop, is in jail, on loan or under contract. Their own silo never turns them away at the door. Children go with a parent, never alone (a child of parents who have parted goes with whichever leaves first; an orphan stays). A refugee who has made a household with someone from the host stays. A family still waiting 455 days after it arrived gives up and settles. Settled refugees are ordinary residents: they no longer count towards crowding, though the silo may still be over its head count, with birth permits at a trickle until the head count catches up.
Where to see it: the log on both sides; the lookup tool's Refugees line on a silo's status (borders, guests and where they are from, the pledge, totals), a Refugee line on a sim's page, and notes in the mesh overview. On the mesh map a silo with its borders open has its airlock doors drawn standing open and a green OPEN TO label; the stricken silo has an EXODUS label with how many have gone, and a host crowded with refugees a CROWDED label with how many it is over.
Food aid: a silo with plenty sends food to a neighbor in crisis.
Sugar: sold to a neighbour whose Spirit Shop is shut or nearly out (see Crops & sugar).
Components: a silo with spare Components may help a struggling neighbor — or refuse, which sours relations (see below). Donors count parts already on the way from other silos and only top a neighbor up to a 20-day reserve, so a dozen silos don't all ship to the same one on the same day. Shipments are at least 10 parts (2 in a seal emergency), so donors don't send a steady trickle of tiny top-ups.
Relations between silos: each silo keeps its own score for every neighbour, from -100 to +100, and they can differ: A may like B while B resents A.
What raises it: help received (food, parts, medicine, water, and most of all repair crews, expert teachers and a silo opening its borders to our families after a disaster), and a little for help given.
What lowers it: a neighbour sitting on spare parts for weeks while we go short, ignoring us in a crisis while it has plenty, and turning our families away at its border. Old permanent grudges from existing saves became a mild "cool" that fades on its own.
Drift: scores fade back towards neutral (a half-life of about 460 days), so old favours are forgotten and old wounds heal.
Kin: two silos with the same naming tradition count each other as kin. The day a silo learns a neighbour shares its tradition it warms to it by 20 points, and from then on its score for that neighbour fades back towards +20 (friendly) rather than towards neutral. Kin can still fall out: refusals and closed borders count against them like anyone else.
Crises count double: help that arrives while a silo is short of food, water or medicine counts twice. A neighbour with plenty that sends nothing for 10 days of such a crisis loses a little standing every day it goes on.
Levels: ally (40+), friendly (15+), neutral, cool (-15 or less), hostile (-40 or less).
What it changes: allies are helped first, looking a little needier than they are, and friendly neighbours (kin among them) a little ahead of strangers. A cool neighbour is helped only some days. A hostile one gets nothing except in a real emergency: under 3 days of food, an outbreak or under 3 days of medicine, a nearly dry reservoir, or a seal emergency (and even then repair crews come more slowly).
Where to see it: the log announces new alliances, hostilities and thaws. The lookup tool shows a Relations line on the silo status, and A relations shows both sides of every relationship. The dashboard has a Relations row. The mesh map draws faint green arcs between allies and red dashed arcs between rivals, lists allies and rivals on hover, and highlights them with the silo's routes. The health check lists allied and hostile pairs and flags any silo being frozen out.
Editing: the CLI editor's edit-colony --set-relation B 50 sets one directly, --set-grudge B makes a silo hostile towards B, and --clear-grudges forgives every neighbour it feels badly about.
Medicine: sold to neighbors running low, and given free during an outbreak if they can't pay. "Low" means under 15 days (20 during an outbreak) of what their stock must cover after their own Pharmacists' daily output, so a silo that makes most of what it uses isn't sent aid. Donors count doses already on the way, so several don't ship at once.
One delivery guard for everything: food, parts, medicine and water donors all count what's already on the way to a silo (from every neighbour) and only top it up to a safe level; repair crews stop at two per silo in an emergency. Founders and newcomers from outside arrive with $600–$1,500 in savings.
Repair crews: a silo with healthy seals lends a few Structural Engineers to a neighbor in a seal emergency. They work there for three to five weeks, then come home.
Water: a small trickle to a neighbor that's nearly dry (about a tenth of a day's use, from all neighbors together), and only on 10 days out of any 30. Each silo relies mostly on its own supply.
Contagion: sick migrants can carry an outbreak across.
Border closures: a silo may turn arrivals away during an outbreak, a toxic waste crisis or under an Isolationist president. Anyone turned away is sent back home through the same airlock, and home always lets its own back in ("Turned away at the border of Silo I, and came home").
Silos share nothing but small files in a shared folder. Each silo publishes a small summary of itself (silo_x_state.json.peer.json, a few KB) that its neighbours read, so twenty silos can check on each other every day without re-reading each other's full saves.

Founding traits

A new real-time silo starts with a few modest traits of its own, drawn from its --seed (the same seed always gives the same silo) or at random without one. Each is good, bad or absent, with at most two bad ones per silo:

Water: deep aquifer (+20% groundwater) or shallow wells (-15%).
Soil: rich (+15% farm output) or poor (-15%).
Reactor: modern (-40% meltdown risk) or aging (+60%).
Seals: new (-30% wear) or worn (start at 80%, +40% wear).
Stores: well stocked (+50% starting food, water, medicine and Components) or lean (-40%).
Treasury: wealthy founders (an extra $50,000 on top of the usual $150,000) or no spare parts (no starting Components).
Founders: 80–140 people.

The dashboard's Colony card lists a silo's traits. --no-traits starts a silo with the standard conditions. Silos saved before this existed show as "standard".

Narration & realism details

LLM narration: an optional local LLM (LM Studio or similar) writes varied activity lines, rumors and the newsletter, falling back to built-in text when it isn't available. Activity lines are given the sim's age and one or two recent milestones from their life story (a new marriage, a new baby, an injury), so what they're doing can fit what just happened to them.
Gossip: now and then word goes around about a resident, good or bad, and moves their reputation over the next 5 to 14 days. Half of it is true. When it has run its course the log says how it turned out: a true rumor stands ("✔️ The rumor about … turned out to be true."), and a false one is mostly undone ("❓ Turns out the rumor about … wasn't true after all."). Nothing is said if the person has died or left by then.
Rumors: small facts get retold and distorted until they can cause unrest, damage someone's reputation or slow work.
Naming traditions: a silo's founders settle on one of 24 real-world naming traditions, chosen at random, when the silo is founded, and the silo keeps it for good.
The founders are named in it, first name and surname. So are newcomers from outside the silos, and babies born there get a first name from it. People who move between silos keep their names, and children take their father's surname.
Two silos may settle on the same tradition. They are kin (see Relations between silos).
A baby is never given the first name of a parent or of a living brother or sister, nor a full name that someone alive in the silo already has. Among the names left, the one fewest people there have is used first. (A tradition has 70 to 90 first names for each sex, fewer than a silo has people, so first names do repeat.)
Iceland: no family surnames. A child is the father's first name plus -son or -dottir. Ethiopia: a child's second name is the father's first name.
Poland, Greece and Russia: daughters and wives take the feminine form of a surname (Lebedev, Lebedeva), and sons the masculine. This applies only to that tradition's own surnames; any other surname is passed on unchanged.
Clubs, rivalries, gossip and random everyday events round out colony life.