# DESIGN.md: Signal-style design system

Measured from https://signal.org/ on 2026-10-15 by PikSpec (https://www.pikspec.com). An independent measurement of the rendered page, not Signal's official design system, and not affiliated with Signal.

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 signal.org, measured from the live site: it should feel designed by the same team as signal.org — the same temperament, colour, type and density — for a different product. Never use signal.org'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://signal.org/ — "signal.org" (home page).
- Page frame: a top navigation bar and a footer.
- Content is grouped in cards (4 on the page, up to 2 side by side). Keep cards for grouped content only, not for every section.
- It uses 10 images, 8 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: 3 buttons on one page.
- The page runs about 5 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)
- Mostly neutral: 86% of the page is #FFFFFF and #F6F6F6 and other neutrals; #9DBBF8 (7.2%) and #A5CAD5 (6.4%) fill whole sections.
- #2C6BED is an accent: 0.1% of the page, used for text and lines only. Don't fill large areas with it.
- The largest type (60px Inter) is bold (800).
- Open: text covers 8% of the page. Sections sit about 96px apart.
- Share of the painted page: #FFFFFF 66.9% (dominant, backgrounds); #F6F6F6 12.7% (dominant, backgrounds); #9DBBF8 7.2% (supporting, backgrounds); #A5CAD5 6.4% (supporting, backgrounds); #3C3744 3.1% (detail, backgrounds); #1B1B1B 2.6% (supporting, text); #404654 0.5% (detail, text); #E9E9E9 0.5% (detail, text). Keep accents at these proportions; do not promote them to fills.
- Large images: Photographs, video or raster artwork cover about 31% of the page.
- Type as set (size, weight and tracking measured together; use these pairs): 60px weight 800; 40px weight 800; 28px weight 800; 20px weight 400; 16px weight 400.

1. DESIGN TOKENS — PASTE INTO YOUR GLOBAL CSS
Allowed colours, with how the original uses each. Use no other colour, including in hover states:
- #FFFFFF — 66.9% · backgrounds (var(--color-action))
- #F6F6F6 — 12.7% · backgrounds (var(--color-f6f6f6))
- #9DBBF8 — 7.2% · backgrounds (var(--color-background))
- #A5CAD5 — 6.4% · backgrounds (var(--color-positive))
- #3C3744 — 3.1% · backgrounds (var(--color-3c3744))
- #1B1B1B — 2.6% · text (var(--color-text))
- #404654 — 0.5% · text (var(--color-text-muted))
- #E9E9E9 — 0.5% · text
- #2C6BED — 0.1% · text, lines (var(--color-on-action))
- #EBEAEB — hairlines and grid lines (var(--color-border))
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=Inter:wght@400;600;800&display=swap");
```
Inter is 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: #9DBBF8; /* Background */
  --color-text: #1B1B1B; /* Text */
  --color-text-muted: #404654; /* Text muted */
  --color-border: #EBEAEB; /* Border */
  --color-action: #FFFFFF; /* Action */
  --color-on-action: #2C6BED; /* On action */
  --color-positive: #A5CAD5; /* Positive */
  --color-f6f6f6: #F6F6F6; /* 12.7% of the page, as fills */
  --color-3c3744: #3C3744; /* 3.1% of the page, as fills */
  --font-body: "Inter", sans-serif; /* Inter */
  --font-interface: "BlinkMacSystemFont", sans-serif; /* BlinkMacSystemFont */
  --type-display-large: 60px; /* Display Large, weight 800 */
  --type-display-large-leading: 64px;
  --type-display-small: 40px; /* Display Small, weight 800 */
  --type-display-small-leading: 44px;
  --type-headline: 28px; /* Headline, weight 800 */
  --type-headline-leading: 32px;
  --type-title: 20px; /* Title, weight 400 */
  --type-title-leading: 28px;
  --type-body: 16px; /* Body, weight 400 */
  --type-body-leading: 22px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-12: 48px;
  --space-16: 64px;
  --space-24: 96px;
  --space-30: 120px;
  --radius-md: 8px;
  --radius-xl: 16px;
  --radius-full: 9999px;
  --elevation-1: rgba(51, 51, 51, 0.05) 0px 1.25px 2.5px 0px, rgba(51, 51, 51, 0.05) 0px 2.5px 5px 0px;
  --elevation-2: rgba(0, 0, 0, 0.12) 0px 4px 12px 0px, rgba(0, 0, 0, 0.08) 0px 0px 2px 0px;
  --elevation-3: rgba(9, 10, 12, 0.1) 0px 8px 16px -2px, rgba(9, 10, 12, 0.02) 0px 0px 0px 1px;
  --duration-1: 0.294s;
}
```
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: #9DBBF8;
  --color-text: #1B1B1B;
  --color-text-muted: #404654;
  --color-border: #EBEAEB;
  --color-action: #FFFFFF;
  --color-on-action: #2C6BED;
  --color-positive: #A5CAD5;
  --color-f6f6f6: #F6F6F6;
  --color-3c3744: #3C3744;
  --font-body: "Inter", sans-serif;
  --font-interface: "BlinkMacSystemFont", sans-serif;
  --text-display-large: 60px;
  --text-display-large--line-height: 64px;
  --text-display-small: 40px;
  --text-display-small--line-height: 44px;
  --text-headline: 28px;
  --text-headline--line-height: 32px;
  --text-title: 20px;
  --text-title--line-height: 28px;
  --text-body: 16px;
  --text-body--line-height: 22px;
  --radius-md: 8px;
  --radius-xl: 16px;
  --radius-full: 9999px;
  --shadow-e1: rgba(51, 51, 51, 0.05) 0px 1.25px 2.5px 0px, rgba(51, 51, 51, 0.05) 0px 2.5px 5px 0px;
  --shadow-e2: rgba(0, 0, 0, 0.12) 0px 4px 12px 0px, rgba(0, 0, 0, 0.08) 0px 0px 2px 0px;
  --shadow-e3: rgba(9, 10, 12, 0.1) 0px 8px 16px -2px, rgba(9, 10, 12, 0.02) 0px 0px 0px 1px;
}
```
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)", "text": "var(--color-text)", "text-muted": "var(--color-text-muted)", "border": "var(--color-border)", "action": "var(--color-action)", "on-action": "var(--color-on-action)", "positive": "var(--color-positive)" },
  fontFamily: { "body": ["var(--font-body)"], "interface": ["var(--font-interface)"] },
  borderRadius: { "md": "var(--radius-md)", "xl": "var(--radius-xl)", "full": "var(--radius-full)" },
  boxShadow: { "e1": "var(--elevation-1)", "e2": "var(--elevation-2)", "e3": "var(--elevation-3)" },
}
```

2. BASE STYLES
```css
html { background: var(--color-background); }
body { margin: 0; font-family: var(--font-body); 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: inherit; }
:focus-visible { outline: 2px solid var(--color-action); outline-offset: 2px; }
```

3. COMPONENTS — MATCH THESE EXACTLY
```css
.card { /* Default */
  background: var(--color-action);
  border-radius: var(--radius-xl);
  padding: 30px 30px 30px 30px;
  min-height: 534px;
  box-shadow: var(--elevation-2);
  color: var(--color-text-muted);
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 24px;
}
.nav { /* Default */
  background: var(--color-action);
  padding: 16px 0px 16px 0px;
  min-height: 85px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 24px;
}
.link { /* Inline */
  background: transparent;
  padding: 8px 12px 8px 12px;
  min-height: 52px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 24px;
  /* recorded states: focus-visible, active, focus, hover */
}
.link-2 { /* Inline 2 */
  background: transparent;
  color: #E9E9E9;
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 22px;
  /* recorded states: focus-visible, active, hover */
}
.link-3 { /* Inline 3 */
  background: transparent;
  min-height: 44px;
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 24px;
  /* recorded states: focus-visible, active, hover */
}
.button { /* Primary */
  background: var(--color-action);
  border-radius: var(--radius-md);
  padding: 0px 20px 0px 20px;
  min-height: 50px;
  box-shadow: var(--elevation-1);
  color: var(--color-on-action);
  font-family: var(--font-interface);
  font-size: var(--type-title);
  font-weight: 600;
  line-height: 28px;
  /* recorded states: focus-visible, active, focus, hover */
}
.button-2 { /* Tertiary */
  background: transparent;
  padding: 8px 12px 8px 12px;
  min-height: 52px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body);
  font-weight: 400;
  line-height: 24px;
  /* recorded states: collapsed, focus-visible, active, focus, 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
- Light interface on #9DBBF8. Keep that ground; do not add a dark mode.
- The opening screen carries a large image or video on the middle. Leave a [content: hero image or video] slot there, at least half the screen wide; the opening is not text alone.
- Sections change ground between Action (#FFFFFF), Background (#9DBBF8), #F6F6F6 and #3C3744; use only those.
- #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: Inter for body; BlinkMacSystemFont for interface. Hierarchy comes from size and weight, not colour or decoration.
- Everything sits on a 4px grid.
- Corner radii are 8px, 16px, fully round (pill) — nothing else.
- Body text uses Inter at around 16px, weights 400, 600, 800.
- Headings use the same family as body text; the largest heading is 60px.
- Primary buttons are #FFFFFF, 8px radius, weight 600.
- Cards use 16px corners with a soft shadow.
- Corner radii in use: 16px, 8px, 9999px (pill).

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 — 680px tall, split 5 / 7, left-aligned 60px heading (weight 800), image centred, on #9DBBF8.
2. Statement — 184px tall, centred 40px heading (weight 800).
3. Split — 764px tall, split 4 / 8, left-aligned 40px heading (weight 800).
4. Split — 1190px tall, 2 equal columns, centred 28px heading (weight 800) set mid-band, image on the left, on #F6F6F6.
5. Split — 635px tall, split 4 / 8, left-aligned 40px heading (weight 800), image on the right.
6. Split — 635px tall, split 8 / 4, left-aligned 40px heading (weight 800), image on the left.
7. Footer — 288px tall, split 5 / 1 / 2 / 2 / 2, left-aligned 16px heading (weight 400), on #3C3744.
- Content sits in a 1344px container, 48px from the edge at 1440px wide.
- A 85px header stays fixed at the top.
- The hero is 680px (0.8 screens): split 5 / 7, left-aligned 60px heading (weight 800), image centred, on #9DBBF8.
- Column splits on a 12-column grid: 4/8 (2×), 5/7, halves, 8/4.
- Headings align left (5 of 7 sections); centre only the occasional statement.
- Sections change background 4 times, between #9DBBF8, #F6F6F6, #3C3744: colour comes in full-width bands, not in boxes.
- A typical section is about 635px tall.

COPY SHAPE (MATCH THE LENGTH AND CASE; WRITE YOUR OWN WORDS)
- The main heading is 2 words long.
- Section headings are short: typically 3 words.
- Headings are in Title Case.

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) ease-out, background-color var(--duration-1) ease-out, border-color var(--duration-1) ease-out, opacity var(--duration-1) ease-out; }
@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 1344px wide, centred, with var(--space-4) (16px) side padding on small screens.
- The largest heading scales fluidly: font-size: clamp(28px, 4.2vw, 60px). 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 (8.9:1), Text muted on Background (4.9:1) and On action on Action (4.7:1).
- 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)
- No gradients: not in backgrounds, text, buttons or borders. (No gradient was measured.)
- Only these colours: #FFFFFF, #F6F6F6, #9DBBF8, #A5CAD5, #3C3744, #1B1B1B, #404654, #E9E9E9, #2C6BED, #EBEAEB. 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.)
- #2C6BED only for text and lines — never as a section background or a large panel. (It covers 0.1% of the page.)
- Only the fonts in the tokens: Inter for body; BlinkMacSystemFont for interface. No other typeface, and no Inter, Roboto or system UI font unless it is one of these. (The page is set in Inter and BlinkMacSystemFont; the tokens carry what stands in for them.)
- The largest headlines are heavy (weight 800). Keep them that heavy, and keep smaller text at the weights in the type scale. (The page sets its biggest type at 800.)
- No all-caps eyebrow labels above headings. (No uppercase text was measured.)
- 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, 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.
- No shadows other than the levels listed.
- Do not use signal.org'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.
- #2C6BED covers about 0.1% of the page or less, as on the original.
- The largest headline is set at weight 800.
- Every section, including ones the original does not have, uses only this system's colours, type, shapes and spacing.
- Content sits in a 1344px container with 48px 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.