one dataset · paper, tables, graph, wiki
simgrammar the grammar of simulation

core loop

dig and build rooms in the vault cross-section -> drag dwellers into rooms matching their SPECIAL stats -> rooms produce power, food, and water on timed cycles -> rush a cycle at the risk of an incident -> recruit, rescue, and breed dwellers -> population thresholds unlock rooms and stronger attackers

design notes

Fallout Shelter is a side-on cross-section of an underground vault built downward from the door, with elevators linking floors. Each production room reads one SPECIAL stat (Strength for power), and dwellers with more of that stat finish its cycle faster; adjacent rooms of the same type and level merge up to three wide, which raises output and cuts the upgrade cost per room. Power is shed by distance: when supply falls short, rooms farthest from the power sources stop first. Rushing a room completes its cycle at once but can trigger an incident; incidents also fire from a background timer whose chance rises until one is guaranteed, spread only from empty rooms to neighbours without revisiting a room, and grow stronger with average dweller level, room level, and room width. Dweller happiness settles at 50 percent, or 75 percent in a room matching the dweller's best stat, rises with successful rushes and breeding, and falls with injury, radiation, and bodies left in the vault. Wasteland exploration sends one dweller out alone for hours of real time to fight and collect caps, junk, weapons, and outfits, spending the stimpaks and RadAway they carry, until recalled, full, or dead (proposed as timed-expedition). When it loads, the game generates what happened while it was closed from the device clock and the last played time, but incidents only occur while it runs in the foreground.

relations

19 stored edges
influenced by
uses

Agent skills

Each dweller has seven SPECIAL stats that training rooms raise one point at a time to 10; the matching stat sets production speed, and level-ups add health scaled by Endurance.

core
uses

Goods consumption

Dwellers draw down vault stocks of food and water; shortages injure and irradiate dwellers and lower their happiness.

core
uses

Power grid

Power generators staffed by high-Strength dwellers supply almost every room; when output falls short, rooms stop working starting with those farthest from the power sources.

core
uses

Romance and family

An adult man and woman placed in living quarters meet, talk, dance, and mate; related dwellers other than cousins, aunts, uncles, nephews, and nieces cannot mate.

core
uses

Adaptive threat scaling

Incident and attack strength rises with the vault's average dweller level and with the level and width of the room under attack, and each attacker type appears only above a population threshold.

supporting
uses

Building placement

Rooms are dug into the rock on a grid next to existing rooms and elevators, and matching rooms placed side by side merge into double and triple rooms.

supporting
uses

Hand crafting

A 2016 update added workshop rooms that craft weapons and outfits from scavenged junk using found recipes.

supporting
uses

Lifecycle and aging

Pregnant dwellers give birth only when the vault has space, and children wander the vault for three hours before becoming assignable adults.

supporting
uses

Milestone unlocks

Room types unlock as the dweller population passes thresholds, such as the Nuclear Reactor at 60 dwellers.

supporting
uses

Permadeath

In survival mode dead dwellers cannot be revived; in normal mode they can be revived for caps.

supporting
uses

Raid defense

Raiders, feral ghouls, and deathclaws attack from outside through the vault door, and dwellers armed with scavenged weapons fight them in the rooms they reach.

supporting
uses

Random disasters

Fires, radroaches, mole rats, and radscorpions break out from a background timer or a failed rush and spread from empty rooms to adjacent ones.

supporting
uses

Real-time clock

On load the game computes everything that happened since the last session from the device clock, so changing the device time breaks room timers.

supporting
uses

Trait inheritance

A child has a 50 percent chance of inheriting either parent's highest SPECIAL stat, and parents with maxed stats can produce children with far higher stat totals.

supporting
uses

Unit commands

The player drags individual dwellers into rooms, out to the wasteland, or into a room with an incident; dwellers do not choose their own jobs.

supporting
uses

Vertical layers

The vault is a stack of underground floors connected by elevator shafts, with the vault door at the top.

supporting

claims

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Fallout Shelter was developed by Bethesda Game Studios with help from Behaviour Interactive.

developed by Bethesda Game Studios, with assistance by Behaviour Interactive

lead

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Bethesda Softworks announced Fallout Shelter, a free-to-play iOS game, at its E3 2015 press conference.

Bethesda Softworks announced the free-to-play Fallout Shelter for iOS during its E3 2015 press conference.

first paragraph

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The iOS version was released on the day it was announced, 2015-06-14.

would be released for iOS the same day

Development

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Pete Hines named Little Computer People, Progress Quest, XCOM, SimCity, and FTL as inspirations.

Little Computer People, Progress Quest, XCOM, SimCity and FTL: Faster Than Light

Development

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Pairing a male and a female dweller in living quarters produces children.

by pairing a male and a female dweller in living quarters to produce children

Gameplay

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Rushing a room risks triggering an incident.

instead having the option to rush the room at the risk of triggering an incident

Gameplay

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When power runs short, rooms stop working starting with those farthest from the power sources.

other rooms will stop producing resources/working, starting with the rooms furthest from the power sources

Fallout Shelter section

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A child has a 50 percent chance of inheriting either parent's highest SPECIAL stat.

Children have a 50% chance of inheriting the 'proficiency' (highest SPECIAL attribute) of either parent.

Breeding

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Children become assignable adults three hours after birth.

After three hours from a Vault dweller's birth, they will become an adult and thus be assignable.

Breeding

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Incidents and attacks grow stronger as the vault's average dweller level rises.

get significantly stronger as your average dweller level increases

Difficulty scaling

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Incidents spread only from rooms with no dwellers in them.

Incidents only spread when a room is empty

Spreading

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Dweller happiness settles at 50 percent by default.

Dwellers normally stabilize at 50% happiness

Section 4, happiness

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Keeping enough food and water in stock prevents dwellers from becoming injured or irradiated.

Be sure to have enough food and water to avoid either of those things happening

Section 4, happiness

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Elapsed time is computed from the device clock when the game is loaded.

The game calculates everything when you load it up based on the current device time

1.1

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The Steam edition lists Bethesda Game Studios as developer and describes building a vault and keeping dwellers happy.

Build the perfect Vault, keep your Dwellers happy, and protect them from the dangers of the Wasteland.

About This Game

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sources

9
Wikipedia contributors (2026). Fallout Shelter. Wikipedia
Bethesda Game Studios (2017-03-29). Fallout Shelter. Steam
Sal Romano (2015-06-14). Fallout Shelter announced for iOS, out now. Gematsu
Fallout Wiki contributors (2026). Vault dwellers (Fallout Shelter). Fallout Wiki (Fandom)
Fallout Wiki contributors (2026). Power generator. Fallout Wiki (Fandom)
therabidsquirel (2026). The Fallout Shelter FAQ, Section 6: Incidents. GitHub wiki
therabidsquirel (2026). The Fallout Shelter FAQ, Section 10: The Wasteland. GitHub wiki

provenance

runs in log/runs
2026-10-25
created2026-10-25-catalog-game-pilotcatalog