# CTAO Science Portal — design system

Single source of truth for look-and-feel. All values live as tokens in
`src/styles/global.css`; this file states the rules. Brand basis: CTAO Brand
Guidelines (Apr 2024) + techniques observed on ctao.org (nebula motion, generous
spacing, 15/30/60 rounding). No frameworks, no JS for presentation.

## Color tokens (brand-fixed — never add hues)

| Token | Value | Use |
|---|---|---|
| `--galaxy` | `#00004A` | Headings, header/footer/hero bands |
| `--cherenkov` | `#00E4D8` | Accents, flash, CTAs, hero subtitle. Never small text on light bg |
| `--moon` | `#F5F5F5` | Utility surfaces (bands, TOC, chips) |
| `--azure` | `#007AFF` | Focus rings, hover borders (UI only on light) |
| `--indigo` | `#00009C` | Gradient depth, link hover |
| `--text` / `--muted` / `--border` / `--link` | derived | Body ink; `--link #0057C2` is azure darkened to pass AA |

## Typography

| Role | Font | Rule |
|---|---|---|
| h1, h2 | Space Grotesk (`--font-display`) | Headlines ONLY (brand D.3.2) |
| Everything else | Inter (`--font-body`) | Includes h3+, cards, UI |

Always end `font-family` with a generic (`sans-serif`) — lint requirement.

## Spacing scale (fluid; mobile ≈ min, desktop ≈ max)

| Token | Value | Use |
|---|---|---|
| `--gutter` | `clamp(18px, 4vw, 28px)` | Container/menu side padding |
| `--space-s` | `12px` | Chip gaps, small stacks |
| `--space-m` | `20px` | Card/panel padding, grid gaps |
| `--space-l` | `24–40px` | Article top, meta/cover margins, featured body |
| `--space-xl` | `40–72px` | Section rhythm: every `.page` block, footer top |
| `--space-band` | `48–96px` | Hero + auth band vertical padding |

Rule: section/container/card padding comes from this table — no ad-hoc px.
Prose-internal margins (h2/p/blockquote) are content-local and stay as written.

## Radius & elevation

Radius: `--radius 16px` (cards/panels), `--radius-pill` (buttons, chips, inputs).

Only two shadows exist, both Galaxy-tinted (`rgba(0,0,74,…)`):

| Token | Use |
|---|---|
| `--shadow-ambient` | Resting cards, panels, search rows |
| `--shadow-lifted` | Hover/focus cards, dropdowns (suggest, mobile menu), auth card |

Never write a literal `box-shadow`; compose focus rings as
`0 0 0 2px var(--azure), var(--shadow-lifted)`.

## Surfaces

Rhythm per page: Galaxy hero band → content → Galaxy footer (flush, no margin).
White = editorial (news grids, articles). `.band--moon` = service/utility
sections (home Services, /search, /support, /proposals, /dashboard). Cards and
panels are always white and pop against Moon via border + ambient shadow.

## Motion policy (CSS-only, Apple-tier restraint)

ctao.org animates nebula videos under Galaxy vignettes; our translation:

1. **Band nebula** — one `--nebula` stack (Cherenkov .38 / Azure .33 /
   Indigo .80 radial fields) used by hero + auth bands, static and animated
   alike; the animated variant is an oversized pseudo-layer drifting via
   `transform` only, 22s alternate. Clearly visible glow, never neon.
2. **Whole-page ambient** — `.has-ambient::before`: fixed brand-hue wash
   (Cherenkov .16 / Azure .12 / Indigo .10 — visible pastel fields, white
   cards pop against them) drifting on a 60s alternate cycle. Opt-in per page
   via `<Base ambient>`: **home only**. Login's full-viewport auth nebula
   already is its ambient; news/article/utility pages stay calm (reading
   focus). Body text NEVER sits on a moving gradient — cards, panels and
   bands are solid layers above it.
3. One-shot hero `rise` stagger; hover lift/transitions. Nothing else.

Rules:
- ALL `animation`/`transition` declarations live inside the single
  `@media (prefers-reduced-motion: no-preference)` block at the end of
  global.css; the `reduce` block additionally force-disables everything.
- Animate `transform`/`opacity` only (compositor-only, per web.dev/MDN); never
  background-position/box-shadow in keyframes. No `will-change` (animated
  properties are auto-promoted — MDN). No `filter: blur` on large layers and no
  `background-attachment: fixed` (broken on iOS) — the wash is a fixed-position
  layer with pre-blurred radial gradients. No JS, no scroll-triggered motion.
- Static gradients remain as the reduced-motion fallback (bands swap them for
  the animated layer — never both, keeping contrast bounded; the ambient wash
  simply stops moving).
- If an effect calls attention to itself as an effect, cut it.

## WCAG 2.1 AA notes (computed, worst-case animation frames)

- Nebula blob peaks over Galaxy: Cherenkov α=.38 → white 7.9:1, Cherenkov
  subtitle 4.9:1, eyebrow `#C7CDE9` 5.0:1. Azure α=.33 → all ≥ 7.7:1.
  Indigo α=.80 → all ≥ 9.6:1. Cherenkov/Azure CORES must stay in opposite
  corners (core-over-core would fail; fringe overlap ≈ 6:1).
- On Moon: `--link` 6.1:1, `--muted` 7.1:1, `--text` 16.9:1.
- Ambient wash worst overlap (`rgb(188,237,249)`): `--link` 5.3:1, `--muted`
  6.2:1, Galaxy h2 15.2:1.
- Ceilings: nebula ≤ .38 Cherenkov / ≤ .35 Azure; wash ≤ .16/.12/.10 —
  recompute (WCAG relative luminance) if any alpha or hue placement changes.
- Focus visible everywhere; tap targets ≥ 44px; skip link first.

## Article TOC pattern

Rendered only when ≥3 h2/h3. Two renderings of the same list (only one ever
displayed): `<details class="toc toc--inline">` collapsed under the title
(< 1200px) and `<nav class="toc toc--rail">` sticky right rail (≥ 1200px,
outside the 70ch column via `.article-layout` grid). MDN/Stripe/NN-g pattern.

## Do not

- No new hues, tints, or grays — derive via `color-mix` from brand tokens only.
- No Space Grotesk outside h1/h2. No dark theme.
- No ad-hoc spacing/shadow/radius values; extend the token tables instead.
- No animation/transition outside the `no-preference` block; no JS motion.
- No dependencies/frameworks (CSS or JS). No removal of "Mock" badges.
- Don't lighten text over navy bands below the alphas listed above.
- No clip-path/CSS approximations of brand assets — the flash is the real SVG
  path from the official logo, or nothing.
- Decoration budget: max ONE accent element per view (currently: footer flash,
  static). No twinkles, floating shapes, or stacked decorations.