# DESIGN.md: GitHub-style design system

Measured from https://github.com/ on 2026-10-14 by PikSpec (https://www.pikspec.com). An independent measurement of the rendered page, not GitHub's official design system, and not affiliated with GitHub.

Use it to build your own product in this design language: put this file in your project root and tell your AI tool (Claude Code, Cursor, Codex, Lovable, v0) to follow DESIGN.md. Never use the original's name, logo, copy or images; licensed fonts are replaced with the closest free Google Fonts.

To capture any other page, or get a ready project for your tool: https://www.pikspec.com/build-with-ai

HOW IT SHOULD LOOK
Build it in the design language of github.com, measured from the live site: it should feel designed by the same team as github.com — the same temperament, colour, type and density — for a different product. Never use github.com's name, logo, words or images.

Stack: use the one your project already has. Starting fresh: React + Vite + TypeScript + Tailwind CSS v4, with no UI kit (no shadcn/ui, MUI or Chakra) — their defaults would override this system. In a chat that shows one file (an artifact or canvas), build one HTML file instead, with the tokens below in its <style> block.
Use every value exactly as written. Do not round, rename, approximate or substitute a colour, size, radius, shadow or easing (fonts: see section 1). Anything not listed here does not exist in this system.

THE WEBSITE THIS SYSTEM COMES FROM
- Reference page: https://github.com/ — "github.com" (home page).
- Page frame: a top navigation bar and a footer.
- It uses 20 images including 2 videos, 18 of them large. Large, real product imagery is part of the look — leave clearly labelled image slots at those sizes rather than stock photos or abstract 3D shapes.
- Interaction: 36 buttons on one page.
- The page runs about 13 screens long at 1440px wide.
- Density is low: few elements per screen, generous space around each one.

HOW IT LOOKS (WHAT MAKES IT LOOK LIKE ITSELF, BEYOND THE VALUES)
- Almost entirely neutral: 99% of the page is painted in #0D1117 and #000000.
- #A2DAFF is an accent: 0.1% of the page, used for text only. Don't fill large areas with it.
- #08872B is an accent: under 0.1% of the page, as small fills such as buttons and badges. Keep it to small areas.
- The largest type (64px Mona Sans) is regular weight, not bold (425), tracked to -0.035em.
- Open: text covers 9% of the page.
- Structure comes from thin grid lines, not from shadows or filled cards.
- Share of the painted page: #0D1117 61.5% (dominant, backgrounds); #000000 33.6% (dominant, backgrounds); #0F1511 1.7% (detail, backgrounds); #FFFFFF 1.2% (supporting, text); #151A22 1.1% (detail, backgrounds); #A4AEA6 0.6% (supporting, text); #A2DAFF 0.1% (accent, text); #7C8980 0.1% (detail, text). Keep accents at these proportions; do not promote them to fills.
- Hairline grid: 1px lines in #21262D run both across and down the page (53 across, 34 down), dividing it into cells instead of cards.
- Large images: Photographs, video or raster artwork cover about 24% of the page.
- Type as set (size, weight and tracking measured together; use these pairs): 64px weight 425 tracking -0.035em; 48px weight 440; 40px weight 460; 24px weight 600; 22px weight 400; 18px weight 400 tracking 0.01em.

1. DESIGN TOKENS — PASTE INTO YOUR GLOBAL CSS
Allowed colours, with how the original uses each. Use no other colour, including in hover states:
- #0D1117 — 61.5% · backgrounds (var(--color-background))
- #000000 — 33.6% · backgrounds (var(--color-surface))
- #0F1511 — 1.7% · backgrounds (var(--color-0f1511))
- #FFFFFF — 1.2% · text (var(--color-text))
- #151A22 — 1.1% · backgrounds (var(--color-151a22))
- #A4AEA6 — 0.6% · text (var(--color-text-muted))
- #A2DAFF — 0.1% · text (var(--color-link))
- #7C8980 — 0.1% · text
- #21262D — hairlines and grid lines
- #5FED83 — small marks (var(--color-positive))
- #1F2328 — Border (var(--color-border))
- #F85149 — Negative (var(--color-negative))
- #D29922 — Warning (var(--color-warning))
Fonts — put these first in your global CSS (one import per font, so one that fails cannot stop the others):
```css
@import url("https://fonts.googleapis.com/css2?family=Mona+Sans:wght@400;425;440;460;480;500;600;800&display=swap");
@import url("https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;500&display=swap");
```
Font: github.com uses Mona Sans Mono (code) — its own licensed face, not available to download. This kit uses JetBrains Mono for code, the closest free match, already in the tokens. If you own the original, add it with @font-face and it is used first; to use another font, change the --font-* variables.
Mona Sans and Mona Sans VF (Google's Mona Sans) are on Google Fonts and loaded from there.
Keep every size, weight, line height and tracking exactly as listed whichever font renders.
```css
:root {
  --color-background: #0D1117; /* Background */
  --color-surface: #000000; /* Surface */
  --color-text: #FFFFFF; /* Text */
  --color-text-muted: #A4AEA6; /* Text muted */
  --color-border: #1F2328; /* Border */
  --color-action: #FFFFFF; /* Action */
  --color-on-action: #000000; /* On action */
  --color-link: #A2DAFF; /* Link */
  --color-positive: #5FED83; /* Positive */
  --color-negative: #F85149; /* Negative */
  --color-warning: #D29922; /* Warning */
  --color-0f1511: #0F1511; /* 1.7% of the page, as fills */
  --color-151a22: #151A22; /* 1.1% of the page, as fills */
  --font-body: "Mona Sans", "Mona Sans", sans-serif; /* Mona Sans */
  --font-interface: "Mona Sans VF", "Mona Sans", sans-serif; /* Mona Sans VF on the site; Mona Sans renders */
  --font-code: "Mona Sans Mono", "JetBrains Mono", monospace; /* Mona Sans Mono on the site; JetBrains Mono renders */
  --type-display-large: 64px; /* Display Large, weight 425 */
  --type-display-large-leading: 69.12px;
  --type-display-large-tracking: -0.035em;
  --type-display-medium: 48px; /* Display Medium, weight 440 */
  --type-display-medium-leading: 56.64px;
  --type-display-small: 40px; /* Display Small, weight 460 */
  --type-display-small-leading: 48px;
  --type-headline: 24px; /* Headline, weight 600 */
  --type-headline-leading: 36px;
  --type-title-large: 22px; /* Title Large, weight 400 */
  --type-title-large-leading: 30.8px;
  --type-title-small: 18px; /* Title Small, weight 400 */
  --type-title-small-leading: 27px;
  --type-title-small-tracking: 0.01em;
  --type-body-large: 16px; /* Body Large, weight 400 */
  --type-body-large-leading: 24px;
  --type-body-large-tracking: 0.015em;
  --type-body-small: 14px; /* Body Small, weight 400 */
  --type-body-small-leading: 21px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 28px;
  --space-8: 32px;
  --space-10: 40px;
  --space-11: 44px;
  --space-12: 48px;
  --space-16: 64px;
  --space-18: 72px;
  --space-20: 80px;
  --space-24: 96px;
  --space-28: 112px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-2xl: 16px;
  --radius-3xl: 24px;
  --radius-48: 48px; /* component radius */
  --elevation-1: rgb(25, 31, 27) 0px -1px 0px 0px inset;
  --duration-1: 0.08s;
  --duration-2: 0.2s;
  --duration-3: 0.3s;
  --duration-4: 0.48s;
  --duration-5: 0.6s;
  --ease-1: cubic-bezier(0.33, 1, 0.68, 1);
  --ease-2: cubic-bezier(0.165, 0.84, 0.44, 1);
  --ease-3: ease-out;
  --ease-4: cubic-bezier(0.12, 0.62, 0.12, 0.95);
  --ease-5: ease-in-out;
}
```
Tailwind CSS v4 (the default for new projects): put this after `@import "tailwindcss";`. It removes Tailwind's own palette, so only these colours exist as utilities:
```css
@theme {
  --color-*: initial;
  --color-background: #0D1117;
  --color-surface: #000000;
  --color-text: #FFFFFF;
  --color-text-muted: #A4AEA6;
  --color-border: #1F2328;
  --color-action: #FFFFFF;
  --color-on-action: #000000;
  --color-link: #A2DAFF;
  --color-positive: #5FED83;
  --color-negative: #F85149;
  --color-warning: #D29922;
  --color-0f1511: #0F1511;
  --color-151a22: #151A22;
  --font-body: "Mona Sans", "Mona Sans", sans-serif;
  --font-interface: "Mona Sans VF", "Mona Sans", sans-serif;
  --font-code: "Mona Sans Mono", "JetBrains Mono", monospace;
  --text-display-large: 64px;
  --text-display-large--line-height: 69.12px;
  --text-display-large--letter-spacing: -0.035em;
  --text-display-medium: 48px;
  --text-display-medium--line-height: 56.64px;
  --text-display-small: 40px;
  --text-display-small--line-height: 48px;
  --text-headline: 24px;
  --text-headline--line-height: 36px;
  --text-title-large: 22px;
  --text-title-large--line-height: 30.8px;
  --text-title-small: 18px;
  --text-title-small--line-height: 27px;
  --text-title-small--letter-spacing: 0.01em;
  --text-body-large: 16px;
  --text-body-large--line-height: 24px;
  --text-body-large--letter-spacing: 0.015em;
  --text-body-small: 14px;
  --text-body-small--line-height: 21px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-2xl: 16px;
  --radius-3xl: 24px;
  --shadow-e1: rgb(25, 31, 27) 0px -1px 0px 0px inset;
  --ease-1: cubic-bezier(0.33, 1, 0.68, 1);
  --ease-2: cubic-bezier(0.165, 0.84, 0.44, 1);
  --ease-3: ease-out;
  --ease-4: cubic-bezier(0.12, 0.62, 0.12, 0.95);
  --ease-5: ease-in-out;
}
```
Tailwind CSS v3 only: extend the theme with these instead, and use no other palette:
```js
// tailwind.config — theme.extend
{
  colors: { "background": "var(--color-background)", "surface": "var(--color-surface)", "text": "var(--color-text)", "text-muted": "var(--color-text-muted)", "border": "var(--color-border)", "action": "var(--color-action)", "on-action": "var(--color-on-action)", "link": "var(--color-link)", "positive": "var(--color-positive)", "negative": "var(--color-negative)", "warning": "var(--color-warning)" },
  fontFamily: { "body": ["var(--font-body)"], "interface": ["var(--font-interface)"], "code": ["var(--font-code)"] },
  borderRadius: { "sm": "var(--radius-sm)", "md": "var(--radius-md)", "lg": "var(--radius-lg)", "xl": "var(--radius-xl)", "2xl": "var(--radius-2xl)", "3xl": "var(--radius-3xl)" },
  boxShadow: { "e1": "var(--elevation-1)" },
}
```

2. BASE STYLES
```css
html { background: var(--color-background); }
body { margin: 0; font-family: var(--font-body); font-size: var(--type-body-large); line-height: var(--type-body-large-leading); color: var(--color-text); -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }
h1, h2, h3 { font-family: var(--font-body); margin: 0; }
a { color: var(--color-link); }
:focus-visible { outline: 2px solid var(--color-action); outline-offset: 2px; }
```

3. COMPONENTS — MATCH THESE EXACTLY
```css
.link-2 { /* Inline 2 */
  background: transparent;
  padding: 0px 0px 2px 0px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-small);
  font-weight: 400;
  line-height: 21px;
  /* recorded states: hover, focus, focus-visible */
}
.link-3 { /* Inline 3 */
  background: transparent;
  padding: var(--space-2);
  min-height: 40px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 500;
  line-height: 24px;
  /* recorded states: hover, focus, focus-visible */
}
.nav-2 { /* Alternative 1 */
  background: transparent;
  min-height: 40px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 24px;
}
.nav-3 { /* Alternative 2 */
  background: transparent;
  color: var(--color-text-muted);
  font-family: var(--font-code);
  font-size: 12px;
  font-weight: 500;
  line-height: 18px;
}
.button { /* Primary */
  background: var(--color-action);
  border-radius: var(--radius-md);
  padding: 6px 20px 6px 20px;
  min-height: 45px;
  color: var(--color-on-action);
  font-family: var(--font-body);
  font-size: var(--type-body-small);
  font-weight: 400;
  line-height: 21px;
  /* recorded states: focus, focus-visible, hover, active, disabled */
}
.button-2 { /* Icon */
  color: var(--color-text);
  font-family: var(--font-interface);
  font-size: var(--type-body-small);
  font-weight: 400;
  line-height: 21px;
  /* recorded states: hover, focus, focus-visible */
}
.button-3 { /* Icon 2 */
  background: var(--color-0f1511);
  border: 1px solid #151A22;
  border-radius: var(--radius-48);
  min-height: 32px;
  color: var(--color-text);
  font-family: var(--font-interface);
  font-size: var(--type-body-small);
  font-weight: 400;
  line-height: 21px;
  /* recorded states: focus, focus-visible, hover */
}
```
Where a component lists recorded states, write those states using only the colours above; the capture saw that the state exists, not its values. Never invent a state colour.

4. PAGE COMPOSITION
- Dark interface on #0D1117. Keep that ground; do not add a light mode or alternate section backgrounds the system does not have.
- The opening screen carries a large image or video behind or across the heading. Leave a [content: hero image or video] slot there, at least half the screen wide; the opening is not text alone.
- #FFFFFF is the action colour. Fill the primary action with it and little else — at most one #FFFFFF-filled element per screen; other accents keep to the uses listed above.
- Type: Mona Sans for body; Mona Sans for interface; JetBrains Mono (standing in for Mona Sans Mono) for code. Hierarchy comes from size and weight, not colour or decoration.
- Everything sits on a 4px grid.
- Corner radii are 4px, 6px, 8px, 12px, 16px, 24px — nothing else.
- Body text uses Mona Sans at around 16px, weights 400, 425, 440, 460, 480, 500, 600, 800.
- Headings use the same family as body text; the largest heading is 64px.
- Primary buttons are #FFFFFF, 6px radius, weight 400.
- Cards use 24px 24px 0px 0px corners.
- Corner radii in use: 6px, 60px, 8px, 12px, 24px.

HOW THE ORIGINAL PACES ITS PAGE (BORROW THE RHYTHM — THE OPENING, THE COLOURED BANDS, THE CARD GRIDS — NOT THE LIST; BUILD THE SECTIONS YOUR PRODUCT NEEDS)
1. Hero — 704px tall, left-aligned 24px heading (weight 600), image behind the content, on #151A22.
2. Statement — 258px tall, centred 16px heading (weight 500), image centred.
3. Statement — 121px tall, centred 14px heading (weight 400), image on the right.
4. Statement — 1141px tall, centred 40px heading (weight 460), image centred, on #000000.
5. Split — 576px tall, split 7 / 5, left-aligned 22px heading (weight 400), on #000000.
6. Split — 559px tall, 2 equal columns, left-aligned 22px heading (weight 480), image on the right, on #000000.
7. Split — 1051px tall, 2 equal columns, 24px gap, centred 40px heading (weight 460), image on the right, on #000000.
8. Cards — 837px tall, 3 equal columns, left-aligned 40px heading (weight 500) set low in the band, image on the right, on #000000.
9. Statement — 1128px tall, centred 40px heading (weight 460), image centred, on #000000.
10. Split — 381px tall, 2 equal columns, left-aligned 48px heading (weight 800), on #000000.
11. Split — 559px tall, 2 equal columns, left-aligned 22px heading (weight 480), image on the right, on #000000.
12. Cards — 1148px tall, 3 equal columns, centred 40px heading (weight 460).
13. Full-bleed image — 1076px tall, centred 40px heading (weight 460) set low in the band, image behind the content.
14. Text — 101px tall, left-aligned 48px heading (weight 440).
15. Footer — 911px tall, 4 equal columns, 24px gap, left-aligned 24px heading (weight 600), on #0D1117.
- Content sits in a 1280px container, 129px from the edge at 1440px wide.
- A 72px header stays fixed at the top, transparent over the first section.
- The hero is 704px (0.8 screens): left-aligned 24px heading (weight 600), image behind the content, on #151A22.
- Column splits on a 12-column grid: halves (4×), thirds (2×), 7/5, quarters; gaps of 24px.
- Headings mix left (8) and centred (7) alignment.
- Sections change background 4 times, between #151A22, #000000, #0D1117: colour comes in full-width bands, not in boxes.
- A typical section is about 576px tall.

COPY SHAPE (MATCH THE LENGTH AND CASE; WRITE YOUR OWN WORDS)
- The main heading is 6 words long.
- Section headings are medium length: typically 4 words.
- Headings are in sentence case (only the first word capitalised).
- The page describes itself in about 25 words; keep your intro paragraph to about that length.

5. MOTION
Interactive elements change colour, background, border and opacity with the measured timing. Animate nothing else.
```css
a, button, [role="button"], input { transition: color var(--duration-1) var(--ease-1), background-color var(--duration-1) var(--ease-1), border-color var(--duration-1) var(--ease-1), opacity var(--duration-1) var(--ease-1); }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}
```
No scroll-triggered fade-ins, parallax, typewriter text or bouncing elements.

6. RESPONSIVE
- The design was measured at 1440px wide. Lay it out for that width first, then let it reflow down to 360px.
- Content sits in a column at most 1280px wide, centred, with var(--space-4) (16px) side padding on small screens.
- The largest heading scales fluidly: font-size: clamp(24px, 4.4vw, 64px). Every other size stays fixed.
- Break on composition, not device names: a row of columns drops a column when any column would be narrower than 240px; side-by-side splits stack when either side would be narrower than 320px.
- Spacing steps never change between sizes; use smaller steps from the same list where space is tight.
- On touch screens, every link and button has a hit area of at least 44 × 44px without changing its drawn size.

7. ACCESSIBILITY
- Text pairs that pass for body copy: Text on Background (18.9:1), Text muted on Background (8.3:1), Action on Background (18.9:1), Link on Background (12.6:1), Positive on Background (12.6:1), Negative on Background (5.6:1), Text on Surface (21:1), Text muted on Surface (9.2:1), Action on Surface (21:1), Link on Surface (14:1), Positive on Surface (13.9:1), Negative on Surface (6.3:1) and On action on Action (21:1).
- Use no other text-on-background pairing.
- One h1 per page, headings in order, landmarks (header, nav, main, footer), real buttons and links, a label on every field, alt text on every image, an aria-label on icon-only buttons.
- Every interactive element shows the :focus-visible outline above.

8. DO NOT (THESE ARE WHAT MAKE AI-BUILT SITES LOOK GENERIC)
- Only the one shadow in the tokens, on the components that use them. (1 shadow value was measured; inventing softer ones changes the depth of the page.)
- No gradients: not in backgrounds, text, buttons or borders. (No gradient was measured.)
- Only these colours: #0D1117, #000000, #0F1511, #FFFFFF, #151A22, #A4AEA6, #A2DAFF, #7C8980, #21262D, #5FED83, #1F2328, #F85149, #D29922. No new tints, no Tailwind defaults (slate, indigo, violet). (They are every colour that covers a measurable part of the page, and the colours its lines and drawings use.)
- #A2DAFF only for text — never as a section background or a large panel. (It covers 0.1% of the page.)
- #08872B only as small fills (buttons, badges) — never a section background or a large panel. (It covers under 0.1% of the page.)
- Only the fonts in the tokens: Mona Sans for body; Mona Sans for interface; JetBrains Mono for code. No other typeface, and no Inter, Roboto or system UI font unless it is one of these. (The page is set in Mona Sans and Mona Sans VF and Mona Sans Mono; the tokens carry what stands in for them.)
- Headings and large text never heavier than weight 600. Do not make headlines bold to add emphasis. (Every size from 24px up is set at weight 600 or lighter.)
- Large headlines tracked tight (letter-spacing -0.035em), not at the browser default. (The 64px headline is set at -0.035em.)
- No icon above every feature, no emoji, no decorative blobs, sparkles or glows. (None of these is part of the captured design; they are a coding model's defaults.)
- The hero is left-aligned. Do not centre it. (The captured hero sets its heading on the left.)
- Build the sections your product needs, not the original's list. Give each one this system's look: its kinds of section (hero, statement, split, cards, image, text, footer), its colours, type, shapes and spacing. (The style carries to any kind of site; the original's page was for a different product.)
- No glassmorphism, backdrop blur, glowing orbs, noise blobs or neon outlines.
- No row of three identical feature cards as the default section. Vary the layout from section to section: a split, a list, a single large statement, a table.
- No centred-everything hero with a pill badge, a gradient headline and two buttons. Lead with the most specific thing about the product.
- No filler copy: no "Unlock your potential", "Revolutionize", "Seamless", "Elevate", "Supercharge", "Next-gen" or lorem ipsum. Write plain, specific sentences a real company would publish.
- No made-up statistics, testimonials or customer logos. Leave a clearly marked [content: …] slot instead.
- No radius larger than the largest one listed.
- Do not use github.com's name, logo, copy or images. This is its design system, not its content.

BEFORE YOU FINISH
- Search your code for every colour, font size, spacing value, radius, shadow and easing, and replace anything that is not a variable above.
- Check that no [content: …] slot has been filled with invented facts.
- Search your CSS for gradient(. There should be none.
- Every colour value in your CSS is one of the allowed colours. Nothing else, including in hover states.
- #A2DAFF covers about 0.1% of the page or less, as on the original.
- #08872B covers about 0.1% of the page or less, as on the original.
- No text 24px or larger has a font-weight above 600.
- The largest headline uses letter-spacing -0.035em.
- Every section, including ones the original does not have, uses only this system's colours, type, shapes and spacing.
- Content sits in a 1280px container with 129px side margins at 1440px.
- There is no placeholder copy (lorem ipsum, "Feature one", "Your headline here"). Every word is real.
- Take a screenshot at 1440px and put it beside the original. List every difference in colour, weight, spacing, alignment and imagery, and fix each before finishing. Then check 390px wide: nothing scrolls sideways and no heading runs off the screen.