---
name: design
description: Create and manage project-specific design systems for SaaS applications. Use when starting a new app (CREATE mode), updating an existing design system (MODIFY mode), or building features that need to follow established patterns (WORK WITHIN mode). Outputs to instructions/design-system.md as the single source of truth for all UX/UI decisions.
---

# Design

Manage your app's design system through `instructions/design-system.md` - the single source of truth for all UX/UI work.

## Choose Your Mode

**CREATE** → No design system yet, or extracting from existing code
**MODIFY** → Have a design system, need to update it
**WORK WITHIN** → Have a design system, building features that follow it

---

## CREATE Mode

Generate a new `instructions/design-system.md` from one of these entry points:

### From URL (Reference App)

Analyze a live app and extract its design patterns.

**Tell AI:**
```
Analyze the design system at [URL].
Identify: colors, typography, spacing, component patterns.
Match to recognized framework (shadcn, Material UI, Radix, etc.).
Generate instructions/design-system.md based on this analysis.
```

**Good reference apps:**
- linear.app (minimal, fast, keyboard-focused)
- stripe.com/dashboard (data-heavy, clear hierarchy)
- notion.so (flexible, calm)
- vercel.com (modern, technical)

### From Code (Extract & Audit)

Paste existing source code to extract and document current patterns.

**Tell AI:**
```
Analyze this code and extract the design system:
[paste relevant components, styles, or config files]

Document: colors, typography, spacing, component specs.
Identify inconsistencies (e.g., multiple button heights, conflicting colors).
Generate instructions/design-system.md with recommendations to standardize.
```

**What to paste:**
- Tailwind config or CSS variables
- Button/Input/Card components
- Theme or design token files
- 2-3 representative page components

### From Screenshot

Upload an image as a visual reference.

**Tell AI:**
```
Analyze this screenshot and extract the design system.
Identify: colors, typography, spacing, component patterns.
Match to closest recognized framework.
Generate instructions/design-system.md based on this analysis.
```

**What to screenshot:**
- Dashboard or main app view
- A form or data entry screen
- Navigation (sidebar or topnav)

### From Scratch

Start fresh with guided decisions.

**Tell AI:**
```
Help me create a design system for [app type].
I want it to feel like [reference: minimal/playful/professional/technical].
Primary brand color: [color or "help me choose"].
Generate instructions/design-system.md with sensible defaults.
```

See [LAWSOFUX.md](LAWSOFUX.md) for why certain patterns work better.

---

## MODIFY Mode

Update an existing `instructions/design-system.md`:

### Update Values

Change colors, fonts, or spacing.

**Tell AI:**
```
Update instructions/design-system.md:
- Change primary color from [old] to [new]
- Update font from [old] to [new]
Ensure all related values are updated (hover states, etc.).
```

### Add Patterns

Add new component types not yet documented.

**Tell AI:**
```
Add a [pricing table / data table / modal] pattern to instructions/design-system.md.
Follow existing design system values (colors, spacing, typography).
Reference: [URL or description of what you want]
```

See [COMPONENTS.md](COMPONENTS.md) for common SaaS component patterns.

### Audit & Reconcile

Compare current code to design system, resolve drift.

**Tell AI:**
```
Audit this code against instructions/design-system.md:
[paste code]

Option A: List deviations so I can fix the code
Option B: Update design-system.md to reflect what code actually does
```

**Always identifies:**
- Inconsistent values (3 different grays, 2 button heights)
- Undocumented patterns (components not in design system)
- Unused specs (documented but not implemented)

### Migrate Framework

Transition from one component library to another.

**Tell AI:**
```
Migrate instructions/design-system.md from [Material UI] to [shadcn].
Keep existing colors, typography, and spacing.
Update component specs to match new framework patterns.
```

---

## WORK WITHIN Mode

Reference existing `instructions/design-system.md` when building:

### Build Feature

Follow the system when implementing new UI.

**Tell AI:**
```
Build [feature description].
Follow instructions/design-system.md for all design decisions.
Use the documented colors, typography, spacing, and component patterns.
```

### Review Compliance

Check AI-built code against the system.

**Tell AI:**
```
Review this code for design system compliance:
[paste code]

Check against instructions/design-system.md.
Flag any deviations from documented patterns.
```

### Answer Questions

Quick design decisions.

**Tell AI:**
```
Based on instructions/design-system.md:
- What color should [element] be?
- What spacing between [A] and [B]?
- Which button variant for [action]?
```

---

## Design-System.md Structure

When CREATE mode generates the file, it follows this structure:

```markdown
# Design System

## Reference
- Primary reference: [app name/URL]
- Component library: [shadcn/Material UI/Radix/custom]
- Design philosophy: [minimal/playful/professional/technical]

## Colors

### Brand
- Primary: #XXXXXX
- Primary hover: #XXXXXX

### Gray Scale
- 50: #XXXXXX (backgrounds)
- 100-400: [values]
- 500: #XXXXXX (borders, secondary text)
- 600-800: [values]
- 900: #XXXXXX (primary text)

### Semantic
- Success: #XXXXXX
- Error: #XXXXXX
- Warning: #XXXXXX

## Typography

### Font
- Family: [Inter/SF Pro/etc.]
- Fallback: system-ui, sans-serif

### Scale
- H1: 32px / 1.2 line-height / semibold
- H2: 24px / 1.25 / semibold
- H3: 20px / 1.3 / medium
- Body: 16px / 1.5 / regular
- Small: 14px / 1.5 / regular
- Tiny: 12px / 1.4 / regular

## Spacing

- Base unit: 4px
- Scale: 4, 8, 12, 16, 24, 32, 48, 64
- Component padding: 16px
- Section spacing: 32px
- Card gap: 16px

## Components

### Buttons
| Variant | Background | Text | Height | Padding | Border Radius |
|---------|------------|------|--------|---------|---------------|
| Primary | primary | white | 40px | 16px 24px | 6px |
| Secondary | gray-100 | gray-900 | 40px | 16px 24px | 6px |
| Ghost | transparent | gray-600 | 40px | 16px 24px | 6px |
| Destructive | error | white | 40px | 16px 24px | 6px |

States: hover (darken 10%), active (darken 15%), disabled (opacity 50%)

### Inputs
- Height: 40px
- Border: 1px gray-300
- Border radius: 6px
- Padding: 12px
- Focus: primary border + ring
- Error: error border
- Disabled: gray-100 background

### Cards
- Background: white
- Border: 1px gray-200 OR shadow-sm
- Border radius: 8px
- Padding: 16px or 24px

## Patterns

### Navigation
- Style: [sidebar/topnav/both]
- Width: [if sidebar, e.g., 240px]
- Behavior: [collapsible/fixed/responsive]

### Forms
- Layout: single column, labels above
- Field spacing: 16px
- Button placement: right-aligned
- Validation: inline, on blur

### Tables
- Row height: 48px
- Actions: right side
- Hover: gray-50 background
- Pagination: bottom

## Inconsistencies Found
[If extracted from existing code, list what was found and standardized]
- Example: Found 3 button heights (36px, 40px, 44px) → standardized to 40px
```

---

## User Override

If you already have a `instructions/design-system.md` file, it takes precedence over any generated recommendations. The skill will work within your documented system.

---

## Common Mistakes

| Mistake | Fix |
|---------|-----|
| Building UI without design system | CREATE mode first, then build |
| Inconsistent components | Use MODIFY → Audit & Reconcile |
| "It looks off but I can't say why" | Check compliance against design-system.md |
| Reinventing patterns | Reference [COMPONENTS.md](COMPONENTS.md) for proven SaaS patterns |
| Ignoring UX principles | Reference [LAWSOFUX.md](LAWSOFUX.md) for why patterns work |

---

## Success Looks Like

✅ Every project has `instructions/design-system.md`
✅ AI builds consistent UI without repeated instructions
✅ Design decisions are documented, not guessed
✅ Code audits catch drift before it compounds
✅ New team members/contractors have clear reference