> ## Documentation Index
> Fetch the complete documentation index at: https://archie.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Functional Design defines what the app does and who does it — archetype, user types, features, system services, and system requirements.

Functional Design covers what your app does and who does it. It's the largest of the three specification groups and the one most builders spend the most time on. Five sub-areas:

<CardGroup cols={2}>
  <Card title="Archetype" icon="compass" href="/docs/features/specifications/functional-design/archetype">
    The foundational shape of your app — solution type, commercialization strategy, and pricing details.
  </Card>

  <Card title="User Types" icon="users" href="/docs/features/specifications/functional-design/user-types">
    The personas who use the app and the use cases each one performs.
  </Card>

  <Card title="Features" icon="layer-group" href="/docs/features/specifications/functional-design/features">
    Modules and the features inside them, with user stories, business rules, and acceptance criteria.
  </Card>

  <Card title="System Services" icon="gears" href="/docs/features/specifications/functional-design/system-services">
    Foundational capabilities — auth, payments, notifications, file storage, and more.
  </Card>

  <Card title="System Requirements" icon="shield-check" href="/docs/features/specifications/functional-design/system-requirements">
    Regional, compliance, security, performance, and accessibility requirements.
  </Card>
</CardGroup>

## How Archie pre-fills these

Functional Design specs are generated from your plan. Archetype reads your initial prompt and the plan's recommendations; user types come from the plan's persona section; features come from the plan's modules; system services and requirements are seeded from the relevant plan sections.

Edit any of them in place. Archie stores edits without touching your generated code until you re-run code generation.

## FAQ

<AccordionGroup>
  <Accordion title="Where do I start editing?">
    Most builders start with **User Types** (to confirm Archie has the right personas) and **Features** (to refine the modules and user stories). The rest can usually run on Archie's defaults until you're ready to ship.
  </Accordion>

  <Accordion title="Can I add a brand-new module in Functional Design?">
    Yes. The Features page lets you add modules and features that weren't in the original plan. Adding here doesn't require a plan regeneration.
  </Accordion>

  <Accordion title="Are functional specs separate from visual specs?">
    Yes — they're different surfaces. Functional Design defines behavior; Visual Design defines look and layout. Both feed into the same generation step.
  </Accordion>
</AccordionGroup>