Folder map

ReplicatedStorage
├── Twill
├── Shared
│   ├── Remotes
│   │   └── Shop
│   └── ShopCatalog
├── Client
│   ├── Controllers
│   │   └── ShopController
│   └── Modules
│       └── Shop
│           └── ShopView
└── Assets

ServerScriptService
├── Twill
├── Main
├── Services
│   ├── CoinService
│   └── ShopService
├── Modules
│   ├── PlayerData
│   └── Shop
│       └── Pricing
└── README

ServerStorage
└── Assets

StarterPlayer
└── StarterPlayerScripts
    └── Client

ReplicatedStorage

Every client can read everything here, whether or not the client runs it.

Location	Class	Holds
Twill	ModuleScript	The shared half of the foundation. Installed from a release and never edited.
Shared	Folder	Declarations and pure functions both sides require. No state.
Shared/Remotes	Folder	One ModuleScript per feature, declaring what a client may ask.
Shared/<Feature>Catalog	ModuleScript	The public definitions of one feature: items, levels, names.
Client	Folder	All client code.
Client/Controllers	Folder	One ModuleScript per feature. Lifecycle boots every one.
Client/Modules	Folder	Private client code, in one Folder per feature.
Assets	Folder	Models, interfaces, and sounds made in Studio that both sides use.
Packages	Folder	Third-party packages both sides use. Create it when the first one arrives.

ServerScriptService

No client can read anything here.

Location	Class	Holds
Twill	ModuleScript	The server half of the foundation. Never edited.
Main	Script	The server composition root. Configures the foundation, then boots Services.
Services	Folder	One ModuleScript per feature. Lifecycle boots every one.
Modules	Folder	Private server code and secret definitions, in one Folder per feature.
Modules/PlayerData	ModuleScript	The saved shape of a player, and the owner of each field.
README	ModuleScript	The rules, written for the people who work in the place.
ServerPackages	Folder	Third-party packages only the server uses. Create it when the first one arrives.

Other containers

Location	Class	Holds
ServerStorage/Assets	Folder	Templates only the server may see.
StarterPlayerScripts/Client	LocalScript	The client composition root. Boots Client/Controllers.
StarterGui		Interfaces made in Studio. No scripts.
Workspace		The world. No scripts. Behaviour binds through tags and attributes.
ReplicatedFirst/Loading	Folder	A loading screen, when the game has one. It depends on no game code.

What boots

Lifecycle.Start requires every ModuleScript that is a direct child of the folder it is given. Main gives it Services, and Client gives it Client/Controllers.

Everything in those two folders boots, including a module that only holds data. A Folder inside one of them is not searched. Both facts lead to one rule: a boot folder holds entries and nothing else, and everything an entry needs lives in Modules or Shared.

Names

Thing	Name	Example
Server entry	<Feature>Service	ShopService
Client entry	<Feature>Controller	ShopController
Private code	Modules/<Feature>/<What it decides>	Modules/Shop/Pricing
Remote declarations	Shared/Remotes/<Feature>	Shared/Remotes/Shop
Public definitions	Shared/<Feature>Catalog	Shared/ShopCatalog

Name a private module after the decision it hides: Pricing, DropTable, Matchmaking. A module named Utils, Helpers, or Manager hides no decision, so nothing says what belongs in it.

A name uses letters, digits, and _. No script is named init, and no two siblings differ by letter case alone.

The folder Shared and the module Twill.Shared are unrelated. The folder holds code both sides require. The module sends messages between servers.

Where data goes

Data	Location
Saved player data: template, version, migrations	ServerScriptService/Modules/PlayerData
State for one player during a session	A local table in the service that owns it, cleared from the player’s bag
Public definitions	ReplicatedStorage/Shared/<Feature>Catalog
Secret definitions: drop rates, thresholds	ServerScriptService/Modules/<Feature>
Values tuned while the game is live	Config, with declared defaults
Settings of one object in the world	Attributes on the tagged instance
Templates cloned at run time	ServerStorage/Assets, or ReplicatedStorage/Assets when a client clones them