MozaikaDesign system

Courier — Design System

dark · modern · medium · custom · confidence 92% · deep decode

Courier composes notifications-for-humans-and-agents in GitHub's open-source Mona Sans: 64px/400 white headlines on near-black #0A0A0A, 15-16px body, and barely-there translucent buttons at 6px radius. Inbox UI panels and API snippets alternate like a conversation between designer and developer — messaging infrastructure with its volume knob deliberately at four.

Open in Mozaika →

This is a static, crawlable rendering for search & AI engines. The interactive version — filters, live decode console, copy & export — is at https://mozaika.design/ds/courier.

Tokens

Courier's decoded design system: background #0A0A0A, text #ECECEE, accent #0000EE, link #083218, primary #0000EE; type scale h1 64px / h2 40px / body 14px; 4px spacing base; 12px base radius. The single interactive/action color is #E2E2E2 — used only on interactive or must-notice elements (buttons, links, key highlights), never on large fills.

Color roles

RoleValue
bg#0A0A0A
surface#171717
border#2B2B2C
text#ECECEE
text_muted#969697
primary#0000EE
accent#0000EE
link#083218
secondary#00B046
button_bg#E2E2E2
button_text#0000EE

Using these colors

Typography

Spacing

Radii

Shadow

rgba(0, 0, 0, 0.12) 0px 1px 1px 0px

Shadows (elevation)

Motion

Micro-interactions run at 5000ms (dominant) with ease-in-out.

Button states (measured)

Layout (measured)

Motion choreography (measured)

Load order: span.framer-text×21

Responsive (measured)

Per-section tokens (12)

Export: DESIGN.md

# Courier — Design System

> dark, modern, medium, custom — deep decode (measured live)

Courier composes notifications-for-humans-and-agents in GitHub's open-source Mona Sans: 64px/400 white headlines on near-black #0A0A0A, 15-16px body, and barely-there translucent buttons at 6px radius. Inbox UI panels and API snippets alternate like a conversation between designer and developer — messaging infrastructure with its volume knob deliberately at four.

## Colors

| Role | Value |
|------|-------|
| bg | `#0A0A0A` |
| surface | `#171717` |
| border | `#2B2B2C` |
| text | `#ECECEE` |
| text_muted | `#969697` |
| primary | `#0000EE` |
| accent | `#0000EE` |
| link | `#083218` |
| secondary | `#00B046` |
| button_bg | `#E2E2E2` |
| button_text | `#0000EE` |

**Using these colors**

- **Action color** `#E2E2E2` — the single interactive color; it appears only on things you click or must notice (buttons, key highlights), never on large fills or backgrounds.
- `primary`, `accent` are all `#0000EE` — one role, not several.
- **accent** `#0000EE` — accent for emphasis — keep it rare on the page.
- **link** `#083218` — fails contrast on the background (~1.4:1) — this is a dark UI color, NOT a readable link; use the text or action color for links (verify against the reference).
- **secondary** `#00B046` — optional secondary accent — LOW decode confidence; use rarely (a status color or a single decorative moment) or omit it entirely. Prefer one accent unless the reference clearly shows two.
- **Page coverage** (full-page screenshot pixels): `#0A0A0A` 75.4% · `#1C182A` 16.1% · `#6F6B82` 8.4%

## Typography

- Heading: **Mona Sans** _(free fallback: Newsreader)_
- Body: **Mona Sans Variable** _(free fallback: Newsreader)_

| Role | Size / weight · line-height · tracking |
|------|------------------------------------------|
| hero | 64px / 400 · lh 70px · tracking -1.92px |
| h2 | 40px / 400 · lh 48px · tracking -0.4px |
| body | 16px / 400 · lh 22px · tracking 0.16px |
| small | 14px / 400 · lh 24px · tracking 0.14px |

- Weight ladder: 400 · 500 — use these exact measured weights, not the 400/600 defaults.

> **Fonts —** Mona Sans may be proprietary — safe free fallback: Newsreader (Google Fonts). Mona Sans Variable may be proprietary — safe free fallback: Newsreader (Google Fonts).

## Spacing
- base unit: 4px (inferred from the measured scale)
- measured scale: 4px, 6px, 8px, 10px, 12px, 16px, 20px, 24px, 28px, 40px — snap all gaps/padding to these

## Radius
- base: 12px
- button: 6px
- card: 8px

## Buttons

| Button | Fill / text | Border | Radius | Padding | Font | Shadow |
|--------|-------------|--------|--------|---------|------|--------|
| primary | `rgba(255, 255, 255, 0.88)` / `#0000EE` | none | 6px | 0px 12px 0px 12px | 400 12px | rgba(0, 0, 0, 0.12) 0px 1px 1px 0px |
| secondary | `rgba(255, 255, 255, 0.04)` / `#0000EE` | none | 6px | 0px 12px 0px 12px | 400 12px | rgba(0, 0, 0, 0.12) 0px 1px 1px 0px |

**States (measured, not guessed)**

- primary hover: background `#FFFFFF`
- primary focus: outline `1px auto rgb(16, 16, 16)`
- secondary hover: background `rgba(255, 255, 255, 0.08)`

## Shadows (elevation)
- subtle: `rgba(0, 0, 0, 0.12) 0px 1px 1px 0px`
- card: `rgba(0, 0, 0, 0.25) 0px 0.602187px 0.602187px -1.25px, rgba(0, 0, 0, 0.22) 0px 2.28853px 2.28853px -2.5px, rgba(0, 0, 0, 0.09) 0px 10px 10px -3.75px`
- button: `rgba(0, 0, 0, 0.12) 0px 1px 1px 0px`

## Motion
- durations: 5000ms (dominant)
- easings: `ease-in-out` (dominant)

Micro-interactions use the dominant duration + easing; nothing on the page animates slower than the longest duration above — don't invent springier motion.

## Layout (measured)
- container max 1280px
- nav: 56px relative · bg #0A0A0A

## Motion choreography (measured)
Load order: `span.framer-text`×21 @0ms
- `ul` ×2 — transform translateX(0px)→translateX(1602px) — 13930ms · loops

Rebuild the timeline, not just the durations — order, delays and staggers above are the choreography.

## Responsive (measured)
- breakpoints: 800px · 1000px · 1279px
- mobile (390px): hero 32px · body 12px · nav: inline

## How to apply
Paste the Tailwind `@theme` (or CSS variables) as your base, then build each
section to its spec — verify every color, radius, and font against these tokens.
Hover/focus states, shadows and motion timings above are measured from the live page — match them exactly, don't re-guess them.

---

> **Decoded with Mozaika** — measured live, not guessed. Full decoded design system + one-command install: mozaika.design/ds/courier

Export: Tailwind v4 (@theme)

@theme {
  /* action color #E2E2E2 — the one interactive color; buttons/links/emphasis only, never large fills. */
  --color-bg: #0A0A0A;
  --color-surface: #171717;
  --color-border: #2B2B2C;
  --color-text: #ECECEE;
  --color-text-muted: #969697;
  --color-primary: #0000EE;  /* a brand color — but the call-to-action uses #E2E2E2, not this. */
  --color-accent: #0000EE;  /* accent for emphasis — keep it rare on the page. */
  --color-link: #083218;  /* fails contrast on the background (~1.4:1) — this is a dark UI color, NOT a readable link; use the text or action color for links (verify against the reference). */
  --color-secondary: #00B046;  /* optional secondary accent — LOW decode confidence; use rarely (a status color or a single decorative moment) or omit it entirely. Prefer one accent unless the reference clearly shows two. */
  --color-button-bg: #E2E2E2;  /* primary-button fill — the main call-to-action color. */
  --color-button-text: #0000EE;
  /* fonts: Mona Sans may be proprietary — safe free fallback: Newsreader (Google Fonts). Mona Sans Variable may be proprietary — safe free fallback: Newsreader (Google Fonts). */
  --font-heading: "Mona Sans", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-body: "Mona Sans Variable", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  /* measured weights: 400, 500 — use these, not 400/600 */
  --text-hero: 64px; --font-weight-hero: 400; --leading-hero: 70px; --tracking-hero: -1.92px;
  --text-h2: 40px; --font-weight-h2: 400; --leading-h2: 48px; --tracking-h2: -0.4px;
  --text-body: 16px; --font-weight-body: 400; --leading-body: 22px; --tracking-body: 0.16px;
  --text-small: 14px; --font-weight-small: 400; --leading-small: 24px; --tracking-small: 0.14px;
  --radius-base: 12px;
  --radius-button: 6px;
  --radius-card: 8px;
  --shadow-card: rgba(0, 0, 0, 0.25) 0px 0.602187px 0.602187px -1.25px, rgba(0, 0, 0, 0.22) 0px 2.28853px 2.28853px -2.5px, rgba(0, 0, 0, 0.09) 0px 10px 10px -3.75px;
  --shadow-subtle: rgba(0, 0, 0, 0.12) 0px 1px 1px 0px;
  --color-btn-hover: #FFFFFF;  /* measured primary hover fill */
  --outline-focus: 1px auto rgb(16, 16, 16);  /* measured focus ring */
  --ease-brand: ease-in-out;
  --duration-fast: 5000ms;  /* use: duration-[var(--duration-fast)] */
  --spacing: 4px;  /* measured base — drives the p-*/gap-* scale. steps seen on the page: 4, 6, 8, 10, 12, 16, 20, 24, 28, 40px */
}

Export: CSS variables

:root {
  /* action color #E2E2E2 — the one interactive color; buttons/links/emphasis only, never large fills. */
  --bg: #0A0A0A;
  --surface: #171717;
  --border: #2B2B2C;
  --text: #ECECEE;
  --text-muted: #969697;
  --primary: #0000EE;  /* a brand color — but the call-to-action uses #E2E2E2, not this. */
  --accent: #0000EE;  /* accent for emphasis — keep it rare on the page. */
  --link: #083218;  /* fails contrast on the background (~1.4:1) — this is a dark UI color, NOT a readable link; use the text or action color for links (verify against the reference). */
  --secondary: #00B046;  /* optional secondary accent — LOW decode confidence; use rarely (a status color or a single decorative moment) or omit it entirely. Prefer one accent unless the reference clearly shows two. */
  --button-bg: #E2E2E2;  /* primary-button fill — the main call-to-action color. */
  --button-text: #0000EE;
  --font-heading: "Mona Sans", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-body: "Mona Sans Variable", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --text-hero: 64px; --weight-hero: 400; --leading-hero: 70px; --tracking-hero: -1.92px;
  --text-h2: 40px; --weight-h2: 400; --leading-h2: 48px; --tracking-h2: -0.4px;
  --text-body: 16px; --weight-body: 400; --leading-body: 22px; --tracking-body: 0.16px;
  --text-small: 14px; --weight-small: 400; --leading-small: 24px; --tracking-small: 0.14px;
  --radius: 12px;
  --radius-button: 6px;
  --radius-card: 8px;
  --shadow-card: rgba(0, 0, 0, 0.25) 0px 0.602187px 0.602187px -1.25px, rgba(0, 0, 0, 0.22) 0px 2.28853px 2.28853px -2.5px, rgba(0, 0, 0, 0.09) 0px 10px 10px -3.75px;
  --shadow-subtle: rgba(0, 0, 0, 0.12) 0px 1px 1px 0px;
  --btn-bg-hover: #FFFFFF;
  --focus-ring: 1px auto rgb(16, 16, 16);
  --ease: ease-in-out;
  --duration-fast: 5000ms;
}
/* fonts: Mona Sans may be proprietary — safe free fallback: Newsreader (Google Fonts). Mona Sans Variable may be proprietary — safe free fallback: Newsreader (Google Fonts). */