developer.mozilla.org

DESIGN.md

Narrative design system document — paste directly into Claude Code, Cursor, or Bolt.

---
version: alpha
name: developer.mozilla.org
description: "Light product system built on #ffffff with #ffffff as the primary CTA accent. Type anchored in Inter at 40px / weight 400. Extracted automatically from https://developer.mozilla.org/ — rendered styles via getComputedStyle() + CSS custom properties (token-only values may not be painted)."
narrative: |
  developer.mozilla.org is built on a pure-white canvas (rgb(255,255,255)).
  The system uses rgb(255, 255, 255) as the singular interactive color.
  Sharp 0px corners on CTAs — architectural restraint, engineering precision alongside Inter as the primary typeface.
  Depth comes from borders and surface contrast rather than shadows — a flat, structural elevation model.
  Motion is minimal — a few targeted transitions, no decorative animation.

colors:
  background: "#ffffff"
  surface-1: "#f7f7f8"
  surface-2: "#f7f7f8"
  ink-muted: "#212426"
  ink-subtle: "#212426"
  primary: "#ffffff"
  on-primary: "#111111"
  primary-hover: "#044c9f"
  hairline: "#51565d"

typography:
  display-xl:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 40px
    fontWeight: 400
    lineHeight: 1.5
    letterSpacing: 0
  display-md:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 16px
    fontWeight: 500
    lineHeight: 1.5
    letterSpacing: 0
  body:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 12.8px
    fontWeight: 500
    lineHeight: 1.5
    letterSpacing: 0
  body-sm:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 16px
    fontWeight: 600
    lineHeight: 1.5
    letterSpacing: 0
  caption:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 12.8px
    fontWeight: 500
    lineHeight: 1.5
    letterSpacing: 0
  button:
    fontFamily: "Inter, 'SF Pro Display', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif"
    fontSize: 14px
    fontWeight: 450
    lineHeight: 1
    letterSpacing: 0

rounded:
  none: 0px
  xs: 4px
  sm: 8px
  md: 14px
  lg: 20px
  xl: 32px
  pill: 9999px

spacing:
  xxs: 2px
  xs: 6px
  sm: 12px
  md: 13px
  lg: 27px
  xl: 28px
  xxl: 64px

components:
  button-secondary:
    backgroundColor: "#6b6b6b"
    textColor: "{colors.primary}"
    typography: "{typography.display-md}"
    rounded: "{rounded.none}"
    padding: 1px 6px
  button-ghost:
    backgroundColor: "transparent"
    textColor: "{colors.primary}"
    typography: "{typography.display-md}"
    rounded: "{rounded.none}"
    padding: 8px 11.2px
  button-light--invert:
    backgroundColor: "{colors.surface-2}"
    textColor: "{colors.primary-hover}"
    typography: "{typography.display-md}"
    rounded: "{rounded.none}"
    padding: 12.8px
  card-standard-card:
    backgroundColor: "transparent"
    typography: "{typography.display-md}"
    rounded: "{rounded.sm}"
    padding: 16px

extracted_at: "2026-06-11T06:08:37.603Z"
completeness: 63
scoreVersion: "v2"

---

# Design System — developer.mozilla.org
> Extracted automatically by Prism from https://developer.mozilla.org
> Date: 2026-06-11
> Viewport: Desktop 1440x900 + Mobile 390x844
> Values are extracted, not hand-written: rendered styles via getComputedStyle() + colors declared in CSS custom properties (token-only values are marked `(token)` and may not be painted).


## 0. Design DNA

**Density**: moderate  |  **Motion**: still  |  **Weight**: light  |  **Aesthetic**: product-neutral

| Dimension | Value | Signal |
|---|---|---|
| Canvas | neutral | `#ffffff` |
| Type posture | sans-led (Inter) | "Resources for Developers, by D" |
| Color assertion | dual-accent | #ffffff |
| Whitespace | moderate | section rhythm 48px |
| Interaction | still | 0 keyframes, 1 transitions |
| Radius language | 4px-rounded | from token scale |

**Prism fingerprint**: `neutral-canvas · sans-display · dual-accent · 4px-rounded · still-motion`

> **🤖 TL;DR for AI agents** (read this first — saves you scanning the full doc):
>
> - **Canvas**: `rgb(255,255,255)` is the page background. Every component composits against this.
> - **Accent**: `rgb(255, 255, 255)` for primary CTAs ONLY. Never decorative.
> - **Body type**: 16px (token: `typography.body`). Default for ALL text not in a heading role.
> - **Section rhythm**: 48px between major bands. Card padding: 27px.
> - **Default radius**: 8px on buttons/inputs. Pills (`9999px`) only for icon-buttons or status chips.
> - **Forbidden**: Do NOT introduce heavy box-shadows — this system relies on borders for separation
>
> **Before generating UI**: import this DESIGN.md, scan §2 (Color Palette) + §4 (Components) + §10 (Agent Guide). Skip §11–12 unless extending.

## 1. Visual Theme & Atmosphere

developer.mozilla.org uses a pure-white canvas (`#ffffff`), letting typography, color and imagery carry the visual weight. 

Typography is anchored in **Inter**, deployed with OpenType features enabled globally (`"calt" 0`). These aren't decorative — they're load-bearing: without them, the typeface reverts to its generic state and the design loses its specific texture. 

Body text reads in Black (`#000000`) (contrast ratio 21.0:1, well above WCAG AA). **White** (`#ffffff`) provides interactive distinction without visual aggression. Shadow is absent by design — depth is conveyed through borders, spacing, and color differentiation rather than light simulation. 


**Key Characteristics:**
- Background: White (`#ffffff`)
- Primary typeface: Inter
- Accent: White (`#ffffff`)
- Border: Slate (`#51565d`) — border-based containment
- Custom fonts loaded: Inter, JetBrains Mono, BarlowCondensed-SemiBold

## 2. Color Palette & Roles

### Background & Surface
- **White** (`#ffffff`): Page background (primary)
- **Off-White** (`#f7f7f8`): Surface / elevated background

### Text & Content
- **Black** (`#000000`): Primary body text
- **Near-Black** (`#212426`): Secondary text
- **Near-Black** (`#18191b`): Secondary text
- **Navy Blue** (`#072446`): Secondary text
- **Warm Brown** (`#3f220d`): Secondary text

### Accent & Interactive
- **Cobalt Blue** (`#044c9f`): Interactive / accent
- **Light Blue** (`#a4cefe`): Interactive / accent
- **#febe8f** (`#febe8f`): Interactive / accent
- **Lavender** (`#d8b8ff`): Interactive / accent
- **#70eba3** (`#70eba3`): Interactive / accent

### Border & Divider
- **Light Grey** (`#c3c7cb`): Borders / dividers

### Full Extracted Palette
**17 colors rendered on the page** + **23** more declared in design tokens (CSS custom properties — not necessarily painted). (13 categorized above + 27 additional below.)
Rendered values are read via `getComputedStyle()`; token values come from CSS variable declarations. Third-party logo colors are filtered out.

- `#51565d` — Slate
- `#6b6b6b` — Slate Grey
- `#260e43` — #260e43
- `#0c311c` — Warm Brown
- `#eaf6ef` — Light Gray *(token)*
- `#fef0c3` — Vibrant Yellow *(token)*
- `#574405` — Chocolate *(token)*
- `#e2782c` — #e2782c *(token)*
- `#fef3eb` — Warm Cream *(token)*
- `#b7102c` — #b7102c *(token)*
- `#fc7d92` — #fc7d92 *(token)*
- `#4b0b16` — #4b0b16 *(token)*
- `#edeef0` — Off-White *(token)*
- `#065b29` — #065b29 *(token)*
- `#2d3034` — Charcoal *(token)*
- `#f7f0ff` — Ghost White *(token)*
- `#ecf4fe` — Ghost White *(token)*
- `#0a5dbd` — M Tricolor Blue *(token)*
- `#5f1fad` — #5f1fad *(token)*
- `#c2570a` — #c2570a *(token)*
- `#089141` — #089141 *(token)*
- `#97770c` — #97770c *(token)*
- `#ffe6ea` — Soft Pink *(token)*
- `#e6b30a` — Amber *(token)*
- `#863ae4` — Violet *(token)*
- `#d31232` — Crimson *(token)*
- `#fae49e` — #fae49e *(token)*

### CSS Custom Properties (Design Tokens)

**Success**
- `--color-green-90`: `#eaf6ef`
- `--color-green-80`: `#70eba3`
- `--color-green-50`: `#089141`
- `--color-green-20`: `#065b29`

**Z-Index Token**
- `--z-index-sticky-header`: `100`
- `--z-index-sidebar-mobile`: `90`

**Background**
- `--color-background-yellow`: `light-dark(#fef0c3,#574405)`
- `--color-background-orange`: `light-dark(#fef3eb,#3f220d)`
- `--color-background-page`: `light-dark(#fff,#18191b)`
- `--color-background-red`: `light-dark(#ffe6ea,#4b0b16)`

**Text Color**
- `--color-text-blue`: `light-dark(#044c9f,#a4cefe)`
- `--color-text-secondary`: `light-dark(#51565d,#c3c7cb)`
- `--color-text-red`: `light-dark(#b7102c,#fc7d92)`
- `--color-text-green`: `light-dark(#065b29,#70eba3)`

**Font Family Token**
- `--font-family-code`: `"JetBrains Mono",monospace`
- `--font-family-text`: `"Inter",sans-serif`

**Error / Destructive**
- `--color-red-10`: `#4b0b16`
- `--color-red-90`: `#ffe6ea`
- `--color-red-20`: `#b7102c`
- `--color-red-50`: `#d31232`

**Border**
- `--color-border-primary`: `light-dark(#c3c7cb,#51565d)`
- `--color-border-secondary`: `light-dark(#51565d,#c3c7cb)`
- `--color-border-active`: `light-dark(#0a5dbd,#a4cefe)`

**Spacing Token**
- `--layout-side-padding-min`: `1rem`
- `--layout-side-padding`: `max(1rem,calc(50vw - 720px + 1rem))`
- `--layout-sidebar-gap`: `2rem`
- `--layout-sidebar-padding`: `1rem`

**Border Radius Token**
- `--radius-normal`: `0.25rem`
- `--radius-full`: `9999px`

**Font Weight Token**
- `--font-weight-bold`: `600`
- `--font-weight-normal`: `400`

**Warning**
- `--color-yellow-90`: `#fef0c3`
- `--color-yellow-20`: `#97770c`
- `--color-yellow-50`: `#e6b30a`
- `--color-yellow-10`: `#574405`

**Font Size Token**
- `--font-size-small`: `0.8rem`
- `--font-size-large`: `1.5rem`
- `--font-size-medium`: `1.25rem`
- `--font-size-largest`: `2.5rem`

**Other tokens**
- `--font-line-header`: `1.25`
- `--color-orange-10`: `#3f220d`
- `--color-gray-05`: `#18191b`
- `--color-blue-80`: `#a4cefe`
- `--color-scrollbar-thumb`: `light-dark(#00000040,#ffffff40)`
- `--color-orange-50`: `#e2782c`
- `--color-blue-20`: `#044c9f`
- `--color-blue-10`: `#072446`

## 3. Typography Rules

### Font Families
- **Primary**: `Inter`
- **Secondary**: `JetBrains Mono`
- **Font 3**: `BarlowCondensed-SemiBold`

### Custom Fonts Loaded
- **Inter** weight 100 900 (normal)
- **JetBrains Mono** weight 100 800 (normal)
- **BarlowCondensed-SemiBold** weight normal (normal)

### Typography Hierarchy

| Role | Font | Size | Weight | Line Height | Letter Spacing | Notes |
|------|------|------|--------|-------------|----------------|-------|
| Display Hero | Inter | 40px | 400 | 1.5 | normal | Main headline (h1) |
| Sub-heading | Inter | 16px | 500 | 1.5 | normal | Third-level heading (h3) |
| Card Title | Inter | 16px | 400 | 1.5 | normal | Card headings |
| Link Large | Inter | 16px | 600 | 1.5 | normal | Link (16px) — Decoration: none |
| Button | Inter | 14px | 450 | 1 | normal | Button label (14px) |
| Caption / Badge | Inter | 12.8px | 500 | 1.5 | normal | small text (12.8px) |

### Font Weight Scale

CSS custom properties define 2 explicit weight steps:
- `--font-weight-normal`: `400` — Regular
- `--font-weight-bold`: `600` — SemiBold

### Full Font Size Scale

Sizes detected in the design (descending): `40px`, `24px`, `20.80px`, `20px`, `19.20px`, `17.60px`, `16px`, `14px`, `12.80px`

> 5 size(s) detected outside the sampled hierarchy (24px, 20.8px, 20px, 19.2px, 17.6px). These appear on elements not in the sampled set — likely additional display sizes, marketing-section overrides, or third-party-widget styles.

### OpenType & Variable Font Features

The typography uses these OpenType features intentionally — this is a sophisticated type system, not a default fallback:

- **contextual alternates** (`calt`) — connections between letters refined contextually

**Clone instruction:** Enable these in your CSS:
```css
body {
  font-feature-settings: "calt";
}
```

## 4. Component Stylings

### Buttons

**Secondary**
- Background: `#6b6b6b`
- Text: `#ffffff` `{colors.primary}`
- Padding: 1px 6px
- Radius: 0px
- Border: 2px outset rgb(255, 255, 255)
- Font: 16px weight 400
- Use: Secondary action

**Ghost**
- Background: `transparent`
- Text: `#ffffff` `{colors.primary}`
- Padding: 8px 11.2px
- Radius: 0px
- Font: 16px weight 400
- Use: Subtle action, toolbar, nav button

**Light / Invert**
- Background: `#f7f7f8` `{colors.surface-2}`
- Text: `#044c9f` `{colors.primary-hover}`
- Padding: 12.8px
- Radius: 0px
- Font: 16px weight 600
- Use: Bright CTA on dark sections

### Cards & Containers

**Standard Card**
- Background: `transparent`
- Padding: 16px
- Radius: 8px
- Border: 1px solid rgb(195, 199, 203)
- Use: Content containers, listing items


## 4b. Component Behaviors (State Matrix)

### Interaction State Narrative

- **Tab**:
  - **hover:** bg transparent → #072446, text #ffffff → #a4cefe, border changes
- **FooterLink**:
  - **hover:** text #51565d → #000000, border changes

*State transitions extracted via Playwright simulation — exact values in the YAML matrix below.*

```yaml
component-behaviors:
  button:
    default:
      bg: "rgb(107, 107, 107)"
      fg: "rgb(255, 255, 255)"
      border: "2px outset rgb(255, 255, 255)"
  link:
    default:
      bg: "rgb(247, 247, 248)"
      fg: "rgb(4, 76, 159)"
  card:
    default:
      bg: "rgba(0, 0, 0, 0)"
      fg: "rgb(0, 0, 0)"
      border: "1px solid rgb(195, 199, 203)"
  navLink:
    default:
      bg: "rgba(0, 0, 0, 0)"
      fg: "rgb(164, 206, 254)"
  tab:
    default:
      bg: "rgba(0, 0, 0, 0)"
      fg: "rgb(255, 255, 255)"
    hover:
      bg: "rgb(7, 36, 70)"
      fg: "rgb(164, 206, 254)"
  badge:
    default:
      bg: "rgba(0, 0, 0, 0)"
      fg: "rgb(0, 0, 0)"
    hover:
      bg: "transparent"
      fg: "inherit"
  footerLink:
    default:
      bg: "rgba(0, 0, 0, 0)"
      fg: "rgb(81, 86, 93)"
    hover:
      bg: "transparent"
      fg: "rgb(0, 0, 0)"
```

**Agent usage**: Validate generated components against this matrix. If your output's `:hover` state changes properties not listed here, you are off-brand.


## 4c. Component Vocabulary (Closed System)

*This brand uses ONLY the following component vocabulary. Introducing new variants without justification breaks the system's tonal coherence.*

### Buttons
- **3 shape(s)** in this system: `Secondary`, `Ghost`, `Light / Invert`
- **DO NOT introduce new buttons variants** without justification

### Cards & Containers
- **1 shape(s)** in this system: `Standard Card`
- **DO NOT introduce new cards & containers variants** without justification

## 5. Layout Principles

### Layout Type
**hero + sections**

### Grid
Single column, centered content

### Max Width
1200px

### Spacing System
Compact spacing — information density prioritized

| Token | Value |
|-------|-------|
| xxs | 2px |
| xs | 6px |
| sm | 12px |
| md | 13px |
| base | 16px |
| lg | 27px |
| xl | 28px |
| 2xl | 48px |
| 3xl | 64px |

### Border Radius Scale
| Name | Value | Use |
|------|-------|-----|
| None | 0px | No rounding |
| Xs | 4px | Tiny corners (badges, micro elements) |
| Sm | 8px | Buttons, inputs, small elements |
| Md | 14px | Cards, containers |
| Lg | 20px | Large rounded elements, pill segments |
| Xl | 32px | Category strips, featured containers |
| Full | 9999px | Pills, avatars, circular elements |

### Shape Language

| Component | Border Radius |
|-----------|---------------|
| Buttons | `0px` |
| Cards & Containers | `8px` |
| Page Body | `0px` |
| Navigation | `0px` |

**Shape Personality**: Moderate Rounding — Medium corners (4–12px). Modern SaaS standard, neither sharp nor pill.

**Full Radius Spectrum**: 4px, 8px (from `allBorderRadii` scan)


## 5b. Spacing Rhythm Names

*Named spacing tokens with explicit use cases. Use these names in YOUR code instead of raw pixels for consistency.*

| Name | Value | Use case |
|------|-------|----------|
| **hero** | `64px` | Top/bottom of full-bleed hero sections |
| **section** | `28px` | Between major bands (color change, content shift) |
| **subsection** | `27px` | Within a section, between content groups |
| **card** | `13px` | Card padding, list-item spacing |
| **compact** | `12px` | Form fields, tight clusters, badge padding |
| **micro** | `6px` | Icon-text gap, tag inner padding |

**Agent rule**: NEVER hardcode raw pixel values for spacing in generated UI. Always reference these named tokens (`spacing-rhythm.section`, etc.).

## 5c. Widget & Structure Library

Structural patterns extracted from the page DOM — these are the **blueprints** an agent should follow to reproduce the page architecture (not just CSS values).

**4/8 structural patterns detected.**

### Hero Pattern

- **Composition:** left-aligned — 
- **Viewport coverage:** 183px tall (not full-viewport)
- **Heading:** "Resources for Developers, by Developers" — 40px left-aligned
- **Subheading:** "Documenting CSS, HTML, and JavaScript, since 2005."
- **CTAs:** none detected in hero (unusual — agent should verify)
- **Clone instruction:** Reproduce the **left-aligned** layout. Use the heading font-size token at the documented size. Pair the centered text with the hero’s decorative visual (gradient / SVG / hero image — see §9b), not bare text.

### Navigation Pattern

- **Position:** static (scrolls with page)
- **Layout:** logo-left-links-left — Logo and links both on the left (CTAs typically right)
- **Height:** 66px
- **Logo:** ✓ present
- **Nav links:** 2 primary items
- **CTAs in nav:** 0 (no buttons — links only)
- **Search:** ✓ search input visible in nav
- **Clone instruction:** Build a static logo left links left navigation. Link-only — no button styling needed.

### Testimonial Pattern

- **Count:** 1 testimonial blocks
- **Layout:** single-feature
- **Avg quote length:** 289 chars (long-form story)
- **Includes:** ✗ no avatars | ✗ no logos | ✗ no ratings
- **Clone instruction:** Build a single-feature of 1 testimonials.   

### Footer Pattern

- **Columns:** 1
- **Links:** 29 total
- **Height:** 424px
- **Includes:** ✗ no newsletter | ✓ social icons |  ✓ copyright
- **Clone instruction:** Build a 1-column footer with ~29 links per column, social media links, and a copyright line.

## 6. Depth & Elevation

| Level | Treatment | Use |
|-------|-----------|-----|
| Flat (Level 0) | No shadow | Page background, content blocks |

**Shadow Philosophy**: Flat design — no shadows used. Borders and spacing define structure.

## 7. Motion & Interaction

### Keyframe Animation Catalog

| Animation Name | Type | Animated Props | Use Hint |
|----------------|------|----------------|----------|
| `fadeIn` | Custom |  | Element entrance |

### Motion Fingerprint

- **Dominant Easing**: standard CSS easings
- **Animation Library**: 1 unique animation (0 total including variants)

## 8. Do's and Don'ts

### Do
- Use Inter as the primary typeface — it defines the brand personality
- Keep font weights between 400-600 — the system uses a narrow weight range for subtle hierarchy
- Use borders for card containment — this design uses border-based depth, not shadow-based
- Use White (`#ffffff`) as the primary accent — it's the brand's signature interactive color
- Use small 4px radius for buttons — this design system uses subtle rounding, not pill shapes
- Apply 16px padding inside cards — matches the design system's content breathing room
- Use 8px border-radius on cards — consistent with the grid card corners
- Maintain nav height at 66px — consistent vertical space for the navigation bar
- Include a search input directly in the nav — discoverability is a primary UX value here

### Don't
- Don't substitute with generic sans-serif or serif — the custom font carries the brand
- Don't use weight 700 (bold) or above — 600 is the maximum weight in this system
- Don't use heavy box-shadows for cards — borders are the containment mechanism
- Don't introduce additional saturated accent colors — the palette is intentionally controlled
- Don't over-round buttons with pill or large radius — the system uses restrained, sharp-ish corners
- Don't collapse or hide the nav on scroll without an explicit scroll-triggered animation — the design uses fixed nav presence
- Don't make the nav sticky — this design lets it scroll away to maximize content focus
- Don't put a CTA button in the nav — this design uses links only at the top


## 7b. Enforceable Brand Rules

*Structured Do/Don't with reasoning and validation tests. Agents can programmatically verify generated UI.*

```yaml
rules:
  - id: brand-canvas-001
    type: do
    rule: "Always use the page background `rgb(255,255,255)` as the base canvas"
    why: "Every component is designed to composit against this exact tone"
    test: "document.body.style.backgroundColor === 'rgb(255,255,255)'"
  - id: brand-accent-001
    type: do
    rule: "Reserve `rgb(255, 255, 255)` for primary CTAs and brand-mark signals only"
    why: "Single chromatic assertion device — overuse dilutes meaning"
    test: "querySelectorAll('[style*=\"rgb(255, 255, 255)\"]').length <= 3 per fold"
  - id: brand-depth-001
    type: dont
    rule: "Do NOT introduce drop shadows on cards or sections"
    why: "Containment is achieved via borders, not elevation — adding shadows breaks the depth contract"
    test: "getComputedStyle(card).boxShadow === 'none'"
```

## 9. Responsive Behavior

### Breakpoints
| Name | Width | Key Changes |
|------|-------|-------------|
| Mobile | 480px | Single column, compact spacing |
| Mobile Large | 640px | Expanded mobile layout |
| Tablet | 768px | Multi-column grids begin |
| Desktop | 1044px | Full feature layout |
| Desktop | 1104px | Full feature layout |
| Large Desktop | 1441px | Maximum content width |

### Token Diff — Desktop vs Mobile

| Element | Property | Desktop | Mobile |
|---------|----------|---------|--------|
| nav | padding | `12px 16px` | `0px` |
| nav | height | `66px` | `46.3906px` |
| hero | height | `182.797px` | `314.797px` |
| button | padding | `1px 6px` | `11.2px` |
| button | width | `auto` | `46.375px` |
| card | width | `376px` | `343px` |

### Collapsing Strategy
- Navigation: horizontal links → hamburger menu on mobile
- Cards: multi-column → stacked vertical on mobile
- Footer: multi-column → stacked single column on mobile

### Touch Targets
- Buttons: 1px 6px padding
- Navigation: adequate spacing between items
- Interactive elements: minimum 44px touch target recommended

### Collapsing Narrative

How the structural patterns adapt from desktop to mobile (extracted from both viewport extractions):

*No major structural differences detected between desktop and mobile widgets. The same blueprints scale rather than collapse — verify by inspecting actual mobile render.*

## 9b. Visual Tone & Photography

**Tone:** Mixed photography + illustration

A balanced mix of photographic content and vector graphics. Photos likely carry product/lifestyle context while SVG handles icons, logos, and decorative accents.

**Canonical Brand Image (OG):**
- https://developer.mozilla.org/mdn-social-image.46ac2375.png
  *This is the image shown when the site is shared on social media — represents the brand visual essence.*

**Aspect Ratio Distribution:**
- Landscape (1.15–2.3): 1 (100%)
- Portrait (<0.87): 0 (0%)
- Square (0.87–1.15): 0 (0%)

**Media Format Mix:**
- PNG: 1 (logos, transparent UI elements, mockups)
- SVG: 1 (icons, illustrations, decorative geometry)

**Average rendered image size:** 203×128px
**Above-fold image count:** 0 / 1

**Decorative Patterns Detected:**
- 1 large decorative SVG shape (≥200×200px, non-icon) — likely blob/illustration accents

**Clone instruction for decorative work:** Decorative details are subtle — don't over-style; the design relies on restraint.

**Imagery Guidance for clones:**
- Mix photography and illustration intentionally: photos for product/context, vectors for icons + decorative accents.
- Respect the format split — replacing JPGs with illustrations (or vice versa) will shift the brand tone.

## 10. Agent Prompt Guide

### Quick Reference
- Background: White (`#ffffff`)
- Primary text: Black (`#000000`)
- Accent: White (`#ffffff`)
- Border: Slate (`#51565d`)
- Font: Inter
- Body: 16px weight 400

### Example Component Prompts
- "Create a hero section on White background (#ffffff). Headline at 40px Inter weight 400, line-height 1.5, color #000000."
- "Create the primary CTA button: `#ffffff` background, `#ffffff` text, 9999px border-radius, 1px 6px padding, 600 weight, Inter font."
- "Design a card on `transparent` background. Border: 1px solid rgb(195, 199, 203). Radius: 8px. Shadow: none. Padding: 16px."
- "Build navigation: static on `#ffffff`. Inter 16px weight 400 for links."

### Iteration Guide
1. **Canvas**: Set the light canvas to White (`#ffffff`) — every component is composited against this exact base.
2. **Typography**: All type in Inter, weight range 400–600. Never exceed 600 — heavier weights break the brand's tonal restraint.
3. **Accent**: White (`#ffffff`) is the sole interactive color. On hover → Cobalt Blue (`#044c9f`). Use CSS transitions, not opacity/brightness filters.
4. **Shape**: CTAs at `0px`, cards at `8px`. Apply border-radius from the extracted scale only — don't invent intermediate values.
5. **Spacing**: Use the `--ca-space-*` token scale (6px–28px). All padding, margin, and gap values are multiples from this scale — no magic numbers.
6. **Tokens**: Import from §11 CSS Export (`--ca-*` vars). Never hardcode hex values — always reference a token so theming remains consistent.

## 11. CSS Design Tokens Raw Export

*Copy-paste ready `:root {}` block — all values extracted directly from the live site.*

```css
/* Colors */
:root {
  --ca-primary: #ffffff;
  --ca-surface-2: #f7f7f8;
  --ca-ink-subtle: #212426;
  --ca-on-primary: #111111;
  --ca-primary-hover: #044c9f;
  --ca-hairline: #51565d;
}

/* Typography */
:root {
  --ca-font-primary: "Inter", system-ui, sans-serif;
  --ca-text-display: 40px;
  --ca-text-body: 12.8px;
  --ca-text-small: 16px;
  --ca-text-caption: 12.8px;
  --ca-text-button: 14px;
}

/* Spacing & Radius */
:root {
  --ca-space-xxs: 2px;
  --ca-space-xs: 6px;
  --ca-space-sm: 12px;
  --ca-space-md: 13px;
  --ca-space-base: 16px;
  --ca-space-lg: 27px;
  --ca-space-xl: 28px;
  --ca-space-2xl: 48px;
  --ca-space-3xl: 64px;
  --ca-radius-none: 0px;
  --ca-radius-xs: 4px;
  --ca-radius-sm: 8px;
  --ca-radius-md: 14px;
  --ca-radius-lg: 20px;
  --ca-radius-xl: 32px;
  --ca-radius-full: 9999px;
}
```


## 13. Page Structure Skeleton

*The actual layout the source site uses. Reproduce these sections in order to match the site structure.*

```yaml
page-skeleton:
  - section: unknown
    tag: div
    height: 91px
    width: 1425px
    layout: block
    children: 1
    bg: "rgb(33, 36, 38)"
    tone: dark
  - section: header
    tag: header
    height: 98px
    width: 1425px
    layout: block
    children: 3
  - section: hero
    tag: div
    height: 2553px
    width: 1425px
    layout: block
    children: 3
  - section: feature-section
    tag: section
    classes: ["homepage-hero"]
    height: 183px
    width: 589px
    layout: block
    children: 2
  - section: feature-section
    tag: section
    height: 350px
    width: 768px
    layout: block
    children: 2
  - section: feature-section
    tag: section
    height: 398px
    width: 768px
    layout: block
    children: 2
  - section: feature-section
    tag: section
    height: 819px
    width: 768px
    layout: block
    children: 2
  - section: feature-section
    tag: section
    classes: ["homepage-contributor-spotlight"]
    height: 340px
    width: 768px
    layout: flex-row justify=normal
    children: 2
  - section: footer
    tag: div
    height: 514px
    width: 1425px
    layout: block
    children: 2
  - section: footer
    tag: footer
    classes: ["footer"]
    height: 424px
    width: 1425px
    layout: block
    children: 2
    bg: "rgb(247, 247, 248)"
    vertical-padding: ~28px
```

**Agent rule**: rebuild sections in this order (sorted by vertical position). Match the layout primitive (grid N-col / flex direction / block).


## 14. Copy Library (Real Content from Source)

*Actual text content extracted from the live page. Use these strings verbatim when reproducing the site — they carry the brand voice.*

```yaml
copy:
  section-headings:
    - "Featured articles"
    - "Contributor Spotlight"
  sub-headings:
    - "Celebrating 20 years of MDN"
    - "Under the hood of MDN's new frontend"
    - "Image formats: Codecs and compression tools"
  ctas:
    - "HTML"
    - "Get involved"
  navigation:
    - "MDN"
    - "Blog"
```

**Agent rule**: reuse these exact strings when generating UI. Do NOT translate or rephrase — brand voice is preserved through the original wording.


## 15. Asset Inventory (Image Roles & Ratios)

*Image inventory classified by role and aspect ratio. When reproducing the site, allocate this number of assets per role.*

```yaml
assets:
```

**Agent rule**: when generating placeholder images, match these counts and aspect ratios. Use neutral placeholder backgrounds for `product` (e.g. `#f5f5f5`), full-color photography hints for `hero` and `editorial`.


## 16. Component HTML Templates

*Suggested HTML markup for reproducing the key components — based on what was detected in the source DOM.*

### Button (primary action)
```html
<button class="btn btn-primary">
  HTML
</button>
```
_Source pattern detected: padding `8px 11.2px` · radius `0px` · weight `400`_

### Generic Card
```html
<div class="card">
  <!-- content -->
</div>
```
_Source pattern detected: padding `16px` · radius `8px` · shadow `none`_

**Agent rule**: use these markup skeletons as the structural baseline. Apply tokens from §2-3 for visual styling.


## 17. Content Architecture & Resources (Links by Purpose)

*The page's links classified by purpose — the information architecture to reproduce. Categories, featured images, devices and projects are extracted from the rendered DOM, not guessed.*

**By purpose:** **nav** 1 · **product** 1 · **docs** 15 · **blog** 8 · **social** 16 · **legal** 2 · **footer** 12 · **other** 4

**Signals:** 4/59 links carry a featured image · dominant link roles: footer-link (28), inline-link (17), social-link (12).


---
## Extraction Completeness: 63/100 (C)

| Category | Score | Max | Detail |
|----------|-------|-----|--------|
| Colors & Palette | 18 | 25 | 13 named colors |
| Typography | 15 | 20 | 6 roles defined |
| Components | 8 | 20 | 2 specs extracted |
| Motion & Interaction | 10 | 15 | Keyframes (intercepted CSS) |
| CSS Custom Properties | 6 | 10 | 129 vars |
| Responsive Breakpoints | 5 | 5 | 6 breakpoints |
| Variable Fonts | 0 | 5 | None detected |

## 12. Known Gaps & Confidence

Explicit list of what this extraction could NOT capture. Agents should not invent values for these — either skip the feature or use the documented baseline + heuristic fallback.

*Auto-detected extraction limitations — understand before building:*

- **Licensed web fonts (Inter, JetBrains Mono)** — detected but not downloaded. Substitute with your licensed copy or a close fallback (see Typography section for metrics).
- **Sparse component extraction** — fewer than 5 component types detected. Highly dynamic sections (modals, datepickers, carousels) require interaction to render and are not captured in a static pass.

| Category | What's missing | Fallback strategy |
|----------|----------------|-------------------|
| **Hero imagery** | No dominant hero image detected above the fold | Use the canonical brand visual from §9b (OG image) for hero composition |
| **Keyframe animations** | No @keyframes declarations found (transitions only) | Use CSS transitions for state changes; avoid complex scroll-based animations |
| **Form inputs** | No text input fields detected on this page | Use the documented border-radius + accent border on focus; 12-16px padding inside |

### Per-section confidence

| Section | Confidence | Reason |
|---------|------------|--------|
| §1 Visual Theme | High | Body bg extracted via getComputedStyle() |
| §2 Colors | High | 129 CSS vars (semantic naming requires ≥20 for high) |
| §3 Typography | High | 6 typography roles inferred |
| §4 Components | Low | 2 component variants captured |
| §7 Motion | Medium | Transitions only |
| §8 Do's/Don'ts | High | 17 rules generated; design-decisions.json has evidence per rule |
| §9 Responsive | High | 6 breakpoints detected |
| §9b Photography | Medium | 1 images, hero not detected |

## 11.1 CSS Implementation Guide (CSS Interception Engine v2.15+)

*Ready-to-use CSS from Prism's CSS Interception Engine — intercepted directly from the site's CSS files (bypasses CORS). Copy-paste into your `<style>` block.*

### Font Loading

3 font file(s) captured (244KB total). When running `prism add`, fonts are saved to `extractions/developer.mozilla.org/fonts/` and embedded as base64 in the output HTML.

**@font-face declarations to use:**
```css
@font-face {
  font-family: 'Inter';
  /* src: url('/fonts/Inter.woff2') format('woff2'); */
  font-weight: 100 900;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: 'Inter';
  /* src: url('/fonts/Inter.woff2') format('woff2'); */
  font-weight: 100 900;
  font-style: italic;
  font-display: swap;
}
@font-face {
  font-family: 'JetBrains Mono';
  /* src: url('/fonts/JetBrains-Mono.woff2') format('woff2'); */
  font-weight: 100 800;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: 'JetBrains Mono';
  /* src: url('/fonts/JetBrains-Mono.woff2') format('woff2'); */
  font-weight: 100 800;
  font-style: italic;
  font-display: swap;
}
@font-face {
  font-family: 'BarlowCondensed-SemiBold';
  /* src: url('/fonts/BarlowCondensed-SemiBold.woff2') format('woff2'); */
  font-weight: var(--font-weight-bold);
  font-style: normal;
  font-display: block;
}
```

### Keyframe Animations (Intercepted from CSS)

**1 @keyframes found** — these are the real animation definitions:

```
@keyframes fadeIn { ... }
```

<details><summary>Full keyframes CSS (1 animations)</summary>

```css
@keyframes fadeIn {
  0% {
  opacity: 0;
  }
  100% {
  opacity: 1;
  }
}
```
</details>

### Hover State CSS (Intercepted)

**57 hover rule lines** captured from CSS files. Key interactive transitions from real CSS (not inferred):

```css
:is(.homepage-hero a):focus,:is(.homepage-hero a):hover{-webkit-text-decoration:none;text-decoration:none}

:is(.featured-articles a):not(:hover){-webkit-text-decoration:none;text-decoration:none}

:is(.latest-news a):not(:hover){-webkit-text-decoration:none;text-decoration:none}

:is(.recent-contributions a):not(:hover){-webkit-text-decoration:none;text-decoration:none}

.homepage-contributor-spotlight__name:not(:hover){-webkit-text-decoration:none;text-decoration:none}

.navigation__button:hover{background-color:var(--color-background-secondary)}

.menu__tab-button:is([aria-expanded=true],:hover){background-color:var(--menu-tab-background);color:var(--menu-tab-text)}

.menu__tab-link:hover{background-color:var(--menu-tab-background);color:var(--menu-tab-text)}

:is(.menu__panel-content a):hover{-webkit-text-decoration:underline;text-decoration:underline}

:is(:is(.breadcrumbs li) a):not(:hover){-webkit-text-decoration:none;text-decoration:none}

@media (width <= 769px){@media (hover:hover){.breadcrumbs li:not(:nth-last-child(-n+2)){display:none}

.footer__logo:hover{color:var(--color-text-primary)}

:is(.footer__socials a):hover{color:var(--color-text-primary)}

:is(.footer__links a):hover{color:var(--color-text-primary)}

:is(.footer__mozilla a):hover{color:var(--color-text-primary)}

.button[data-variant=primary]:hover{--csstools-light-dark-toggle-33eaa513-2:var(--csstools-color-scheme--light) var(--color-gray-60);background-color:var(--csstools-light-dark-toggle-33eaa513-2,var(--color-gray-40))}

@supports (color:light-dark(red,red)){.button[data-variant=primary]:hover{background-color:light-dark(var(--color-gray-40),var(--color-gray-60))}

.button[data-variant=primary][data-action=positive]:hover{--csstools-light-dark-toggle-33eaa513-4:var(--csstools-color-scheme--light) var(--color-green-50);background-color:var(--csstools-light-dark-toggle-33eaa513-4,var(--color-green-20))}

@supports (color:light-dark(red,red)){.button[data-variant=primary][data-action=positive]:hover{background-color:light-dark(var(--color-green-20),var(--color-green-50))}

.button[data-variant=primary][data-action=negative]:hover{--csstools-light-dark-toggle-33eaa513-6:var(--csstools-color-scheme--light) var(--color-red-50);background-color:var(--csstools-light-dark-toggle-33eaa513-6,var(--color-red-20))}
```

> **Note**: All values above are extracted from the live site's CSS files. The font files are saved locally by Prism and embedded in the output HTML. Use them as-is for maximum fidelity.

## 11.2 Measured Reality (CDP Engine)

Captured directly from Chrome's engine across **all 948 rendered nodes** — not a sample. These are the values the page *actually paints*, weighted by how often they appear.

### Real Responsive Breakpoints
**10 breakpoints** read from the live `@media` rules (not guessed):
`480px` · `640px` · `768px` · `769px` · `840px` · `992px` · `1000px` · `1044px` · `1104px` · `1441px`

### Measured Design Scale
**Type scale by usage** (× = paint count): `16px`×448 · `24px`×172 · `12.8px`×138 · `19.2px`×74 · `20.8px`×65 · `14px`×13 · `12px`×7 · `10px`×6

**Radius scale** (× = paint count): `4px`×10 · `8px`×10 · `9999px`×4

**Weights** (× = paint count): `400`×544 · `300`×336 · `500`×48 · `450`×13 · `600`×4 · `650`×2

**Layout gaps** (× = paint count): `normal 2px`×8 · `normal 16px`×4 · `6px`×3 · `8px`×3 · `12px normal`×3 · `normal 4.375px`×2 · `normal 4px`×2 · `normal 48px`×2

### Provenance — measured styles on key elements
Read from the live CSSOM (includes runtime-injected CSS). This is *what actually styles the page*, by element:

```css
nav { background-color:var(--color-background-page) }
nav { color:var(--color-text-primary) }
h1 { font-size:var(--font-size-largest); font-weight:400 }
h2 { font-size:var(--font-size-large); font-weight:500 }
a { color:var(--color-link-normal) }
a { background-color:var(--color-background-primary); font-weight:var(--font-weight-bold) }
```

> Selectors normalised to their semantic element — source class names are often build-hashed (`.bgDIHX`) and not reusable. The declarations + CSS vars are the transferable part.

---
*Generated by Prism — automated Playwright extraction + design analysis.*
*Source: https://developer.mozilla.org | 2026-06-11T06:08:37.642Z*
*Values extracted via getComputedStyle() (rendered) + CSS custom properties (tokens, marked `(token)`). Token-only values may not be painted — verify against the live site before shipping.*