# Architecture

AI Playgrounds uses a no-build, single-file applet architecture.

## Public surfaces

- `index.html` provides the live demonstration and searchable catalogue.
- `playgrounds/<slug>/index.html` contains one complete applet.
- Teacher, curriculum, student, quality, and citation pages are plain HTML.
- `applets.json` provides shared public metadata for the twelve applets.

## Applet structure

Each applet contains:

1. the primary interactive model,
2. Explore, Understand, Use in class, and Text and keyboard modes,
3. complete English and Chinese interface, explanation, scenario, and accessibility strings,
4. local response-packet tools,
5. shareable URL state whose exact serialized controls override scenario presets,
6. optional analytics restricted to the canonical hosted site.

No applet requires a framework, account, backend, package manager, model download, or remote runtime asset.

## Privacy and portability

Student responses remain in the browser unless the learner copies or prints them. The site has no student accounts, database, upload endpoint, or response-collection backend.

## Visual identity

Each applet has one categorical accent defined in `applets.json`. Color supports recognition but is never the only identifier. Applet names, icons, categories, and sequence numbers remain visible throughout the suite.

## Browser support

The public site is designed for current desktop and mobile browsers. Each applet can also be opened directly from the local filesystem.

## Localization boundary

Public learner and educator content is translated completely. Stable machine and source literals, including URLs, filenames, identifiers, formulas, licenses, names, and standard acronyms, remain unchanged while their visible labels and explanations are localized. See `docs/LOCALIZATION.md`.