# Glass Pen Nib

> Lumen pack asset: a pen nib in frosted, halftone-printed glass, hovering over a separate base bar. Every few seconds it taps down: the bar squashes, the slit flexes open, and the nib springs back up. Raymarched in WebGL with refraction, so the slit and breather hole show their inner walls. Five tints or your own colors. Zero dependencies; any number share one WebGL context.

- Slug: `lumen-pen`
- Category: [Asset packs](https://www.assembli.design/category/asset-packs.md)
- Subcategory: [Lumen](https://www.assembli.design/category/asset-packs/lumen.md) (`lumen`)
- Type: component
- Tags: 3d, webgl, raymarching, asset, glass, icon, pen, nib, design, edit, write
- npm dependencies: none
- shadcn/ui dependencies: none
- Added: 2026-10-21
- Live preview: https://www.assembli.design/preview/lumen-pen
- Page: https://www.assembli.design/components/lumen-pen

## Install

One-time setup (needs a subscription):

1. Add the registry to the project's `components.json`: `{"@assembli":{"url":"https://www.assembli.design/r/{name}.json","headers":{"Authorization":"Bearer ${ASSEMBLI_API_KEY}"}}}` (merge into `"registries"`).
2. Put an API key from https://www.assembli.design/account in `.env.local` as `ASSEMBLI_API_KEY=asm_…`.

Then install with the shadcn CLI (writes `components/lumen-pen/lumen-pen.tsx` and installs dependencies):

```bash
npx shadcn@latest add @assembli/lumen-pen
```

Registry item JSON: https://www.assembli.design/r/lumen-pen.json (send `Authorization: Bearer <api key>`)

## Code

> Component source needs an Assembli subscription ($12/month) and an API key sent as `Authorization: Bearer <key>`. To get one without copying anything, POST https://www.assembli.design/api/agent/login (or call the MCP tool connect_account), show the user the link it returns, and poll https://www.assembli.design/api/agent/token for the key. Or subscribe at https://www.assembli.design/pricing and create a key at https://www.assembli.design/account.