Add a single file browser demo

Nothing to install and nothing to download: index.html is a small standalone
version of the same idea, in about 1600 lines of HTML, CSS and JavaScript
with no dependencies and no build step.

It carries over the parts that matter: the Scratch 3 shapes drawn as SVG
paths from the same puzzle geometry, one continuous drawer that glides
between sections, dragging with snapping, C shaped mouths, reporters that
drop into slots, and the Python appearing live beside you to copy or save.

A small interpreter means Run really works in the page, and clicking a loose
block still reports its answer in a bubble. Each block is described once and
that description drives all three things: how it is drawn, the Python it
generates and how it runs. Pointer events throughout, so a mouse, a pen or a
finger all work.

Twenty six blocks across five categories. Everything else stays in the
desktop app, which the page links to.

The glide and the interpreter step on timers rather than animation frames,
so both still finish properly in a background tab where no frames are drawn.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: 2 people

README.md

@@ -31,6 +31,13 @@ Python standard library**.
 python scratchpy_studio.py
 ```
 
+### 👉 [Try the browser demo](https://zdstudios.github.io/scratchpy-studio/) — no install, nothing to download
+
+[`index.html`](index.html) is a small standalone version of the same idea: one
+file, no dependencies, no build step. Drag blocks, watch the Python appear, press
+Run and it executes right there in the page. It is a taste of the real thing —
+the desktop app has 148 blocks, pip, file handling and the rest.
+
 ---
 
 ## Why it is different
@@ -333,6 +340,32 @@ finally runs the generated example program and checks its output.
 
 ---
 
+## The browser demo
+
+[`index.html`](index.html) is a self-contained demo you can open by
+double-clicking it, or visit at
+**[zdstudios.github.io/scratchpy-studio](https://zdstudios.github.io/scratchpy-studio/)**.
+
+It shares the desktop app's ideas in about 1,600 lines of HTML, CSS and
+JavaScript with **no dependencies and no build step**:
+
+* the same Scratch 3 shapes, drawn as SVG paths from the same puzzle geometry
+* one continuous drawer that glides between sections
+* drag, snap, C-shaped mouths, reporters that drop into slots
+* the Python it makes, updating live beside you — copy it or save it as a `.py`
+* a small interpreter so **Run** actually works in the page, and clicking a loose
+  block still shows its answer in a bubble
+
+Each block is described once, and that single description drives all three
+things: how it is drawn, the Python it generates, and how it runs. It works with
+a mouse, a pen or a finger.
+
+The demo keeps 26 blocks across five categories. Everything else — the other
+120 blocks, pip, the venv, files, the web blocks, the Python importer, the MCP
+server — lives in the desktop app.
+
+---
+
 ## What it puts on disk
 
 | Name | What it holds |