[JGalego]

A retro landing page telling HyperCard's story, and the whole application
running on it — the same renderer the desktop draws, over the same runtime
compiled to WebAssembly.

The playground is the application

The desktop keeps its shell behind one module (apps/desktop/src/api.ts, a
typed wrapper per command), and the renderer never learns which shell
answers. Vite swaps that one module for apps/web/src/api.ts; nothing else
in the desktop tree is touched, so the two interfaces cannot drift apart —
they are the same files. apps/desktop/ has no changes in this diff at all.

Behind it, crates/web wraps the same crates the Tauri shell wraps, one
exported function per desktop command.

What a browser makes hard, and what was done about it

A script has to block on a dialog. ask stops the script and the answer
lands in it on the next line. The runtime lives in a Web Worker; when a
script asks, the worker parks on Atomics.wait while the page — still
responsive — shows the same dialog component the desktop shows, and writes
the reply into a SharedArrayBuffer. The runtime is none the wiser. GitHub
Pages cannot send the isolation headers that needs, so a vendored
coi-serviceworker.js (MIT) adds them, at the cost of one reload on first
visit; without isolation the runtime falls back to the main thread and
window.prompt.

There is no file system. A stack travels as the single-file JSON
hyperlab-persistence already speaks — the same file the desktop opens.

There is no clock. SystemTime::now traps on wasm32, so
hyperlab_stack::set_clock lets a host name one and the web shell names the
browser's. The interpreter's the date and random follow it.

There are no fonts. Artwork carries words — Cluedo's board names its
rooms — and both exporters asked the operating system for a typeface. They
now take one from their host too. Chasing this found a real bug beyond the
browser: usvg resolves the generic families through names of their own, and
sans-serif means Arial until told otherwise, so a stock Linux box with no
Arial was losing labels as surely as a page was. The stand-in now turns on
whether the family resolves, which fixes both and leaves a well-stocked
machine alone.

Keys never leave the browser

The desktop keeps API keys in the OS keychain, one-way. The web keeps the
same shape with the parts a page has: a key goes into this browser's
storage, no command reads one back out, and requests go straight from the
browser to the configured provider. The site is static files, so there is no
server of ours for a key to visit. A mock provider answers locally, so the
whole AI surface can be tried with no key at all.

Feature parity

Everything on the desktop's File menu is here, including a PDF of the cards,
a PNG of the map, a self-contained web page, and a Decker deck. A Cluedo PDF
exported in the browser matches the desktop's checked-in docs/cluedo.pdf:
three pages, thirteen pieces of artwork, the same words, an embedded face
for the labels. The one deliberate difference is Save / Save As…
collapsing into Download Stack.

Enabling changes to existing crates

• hyperlab-ai-providers gained a default-on native feature. Without it
  the crate is only the wire protocol, for a host that brings its own
  transport; with it, nothing changes.
• hyperlab-persistence gained single_file_string and
  stack_from_single_file.
• hyperlab-mcp's client is native-only — it spawns a program, which a
  browser cannot do.
• The Todo example gained the trailing newline its Add button always
  assumed.

Verified

CI is green on 036fe74, all seven jobs. Beyond that, the built site was
driven in Chromium: all six examples open and draw, a script's ask blocks
and its reply reaches it, undo works, the mock assistant answers, ai("…")
answers mid-script, and both new exports produce valid files.

One thing left for a human

Settings ▸ Pages ▸ Source must be set to GitHub Actions before the
deploy workflow has anywhere to publish.

docs/website.md explains the arrangement in full.

🤖 Generated with Claude Code

https://claude.ai/code/session_01R7eaxUAqy2gKQSBNnYZoFr