# Expandable Card (Lumen Halo): prompt.md (v1.0.0)

- id: `lumen-expandable-card` · version 1.0.0 · component · pro (Pro)
- category: Layout
- build: Base UI (one set of files; its dependencies follow the build)
- install (this build): `npx shadcn@latest add @beautiful-ui-pro/lumen-expandable-card`
- npm dependencies: none
- registry dependencies: utils, @beautiful-ui/lumen-dialog, https://beautiful-ui.dev/r/lumen-foundation.json
- docs: https://beautiful-ui.dev/components/lumen-expandable-card
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.

A card that opens into its full story: the detail panel grows out of the card's own outline with the page dimmed behind, and Escape, the close button or a click outside put it back with focus on the card.

## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: none beyond React.
- Files: `components/ui/lumen/controls/expandable-card.tsx`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `lumen-dialog`, `lumen-foundation`.
- Builds: one set of files for both, but its dependencies come in Base UI and Radix builds. Install the one that matches the project (see Install): a free item's bare URL installs the Base UI build of it and its dependencies.
- Exports to keep: `ExpandableCard`, `(media)`, `(panel)`, and every exported type.
- CSS: the install merges this item's rules (the registry `css` field) into your global stylesheet, in `@layer components`, and adds the lumen foundation (tokens, keyframes, motion levels) once. Nothing to import by hand.
- Re-running `add` (or `--overwrite`) re-applies those rules: put overrides in your own CSS, never in the installed rules.
- Tokens: retheme with the `--lumen-*` custom properties (`--lumen-accent`, `--lumen-accent-foreground`, `--lumen-accent-text`, `--lumen-bad`, `--lumen-bad-text`, `--lumen-chart-accent`, `--lumen-chart-accent-foreground`, `--lumen-chart-accent-text`, `--lumen-focus`, `--lumen-good`, `--lumen-good-text`, `--lumen-hairline`, `--lumen-ink`, `--lumen-muted-ink`, `--lumen-series-1`, `--lumen-series-2`, `--lumen-series-3`, `--lumen-series-4`, `--lumen-series-5`, `--lumen-series-6`, `--lumen-warn`, `--lumen-warn-text`); this item's CSS also reads `--lumen-font-mono`, `--lumen-font-sans`, `--lumen-radius-k`. Never add Tailwind colour classes inside the component.

```tsx
import { ExpandableCard } from "@/components/ui/lumen/controls/expandable-card";
```

## Parts

| Part | data-slot | What it is for |
|---|---|---|
| `ExpandableCard` | — | The card (a button). |
| `(media)` | — | The card's artwork. |
| `(panel)` | — | The open panel, a Lumen Dialog. |

## Sound
- Keep every `data-slot` and `data-sound` attribute: the sound layer reads them.
- Installing this item adds no audio. Nothing plays until the app mounts `GlassSoundProvider` once (install: `npx shadcn@latest add https://beautiful-ui.dev/r/glass-sound.json`, import from `@/components/beautiful-ui/glass-sound`); `GlassSoundToggle` is its mute control. Without a provider the audio engine never loads.

## Match the original
- Read `components/ui/lumen/controls/expandable-card.tsx` as the reference implementation before changing or recreating anything, and match it: sizes, colours per theme, motion timings, copy and behaviour.
- If you deviate (a prop you can't honour, a style you changed, a dependency you swapped), say so in your reply, part by part.
- Keep the accessibility contract, the keyboard map and the motion levels listed below.

## Use it when
- expandable card, card expand, card to modal, card detail, grow card, feature card, case study card, gallery card
- A grid of features, case studies, templates or people, where each has more to say than fits on the card
- Browsing: open one, read, close, open the next

### Not when
- Content people need side by side with the page: use Sheet or Detail Drawer
- A card that links to its own page: use a plain link card

## Mistakes
- Don't put buttons or links inside the card: the whole card is one button
- Keep the summary short; the long version goes in children

## Usage

```tsx
"use client";

import { ExpandableCard } from "@/components/ui/lumen/controls/expandable-card";

export function CaseStudies() {
  return (
    <div className="grid gap-4 sm:grid-cols-2">
      <ExpandableCard
        eyebrow="Case study"
        title="Signup, rebuilt"
        description="How a team of four halved drop-off in six weeks."
        media={<img src="/cases/signup.jpg" alt="" />}
      >
        <p>They started by watching ten people sign up, and cut every field nobody needed on day one.</p>
        <p>Drop-off fell from 41% to 19%.</p>
      </ExpandableCard>
    </div>
  );
}
```

## Props

| Prop | Type | Default | What it does |
|---|---|---|---|
| `title` | `ReactNode` |  | On the card, and the panel's title. |
| `description` | `ReactNode` |  | The summary on the card, and the panel's description. |
| `eyebrow` | `ReactNode` |  | A small label above the title. |
| `media` | `ReactNode` |  | Artwork at the top of the card, larger in the panel. Give images alt="": the title names them. |
| `children` | `ReactNode` |  | The detail, rendered only while open. |
| `open / defaultOpen / onOpenChange` | `boolean / boolean / (open: boolean) => void` |  | Controlled or uncontrolled. |
| `panelClassName` | `string` |  | Classes for the open panel. |

Full docs: https://beautiful-ui.dev/components/lumen-expandable-card

## Customising
- Colours: set the `--lumen-*` tokens on `:root`, or on a container with the `lumen-scope` class to retheme one area. Add the `lumen-inherit` class to follow your shadcn palette instead (`--chart-N`, `--destructive`).
- Dark mode follows the `.dark` class on an ancestor (the shadcn and next-themes convention).
- Update later by re-running the install with `--overwrite` (review the diff if you edited it). Changelog: https://beautiful-ui.dev/r/changelog.json

## Keyboard

| Keys | Action |
|---|---|
| Enter or Space | Open (on the card) |
| Tab | Moves within the open panel |
| Escape | Close |

## Motion inventory

| Interaction | What moves |
|---|---|
| Open | The panel is revealed from the card's rectangle to its own in 480ms, nothing stretched; the text rises in after. Reduced motion fades |
| Hover | The card lifts 1px and its plus turns |

## Accessibility contract (preserve when editing)
- The card is a button that says it opens a dialog (aria-haspopup, aria-expanded)
- The panel is a Dialog named by the title and described by the summary; focus stays inside until it closes
- Focus returns to the card however it closed

## Install

```bash
npx shadcn@latest add @beautiful-ui-pro/lumen-expandable-card
```

Pro item: needs the `@beautiful-ui-pro` registry in `components.json` and `BEAUTIFUL_UI_TOKEN` in `.env.local` (https://beautiful-ui.dev/account). Setup: https://beautiful-ui.dev/docs/pro. Your components.json `style` picks the build: radix-*, new-york and default get Radix, base-* gets Base UI.

## Credits
- Built on shadcn/ui (https://ui.shadcn.com)

The lumen foundation (the tokens listed above, keyframes and motion levels) installs once with the first component; its CSS is public at https://beautiful-ui.dev/r/lumen-foundation.json.