Browser demo reads Python, and grows to 95 blocks

Two things the demo could not do: it had a small handful of blocks, and it
could only be built by hand.

Reading Python in a browser means no ast module, so this adds a tokeniser
and a recursive descent parser written from scratch in JavaScript. It
handles indentation, strings including triple quoted and f-strings, joined
lines, and the usual precedence ladder. On top of that sits a mapper to
blocks that understands assignments, if/elif/else, while, for over range and
over lists, def with parameters and returns, break, continue, comparisons,
and/or/not, list and string methods and the built-ins people actually use.
Functions arrive as real custom blocks with a define hat and a call block.
Anything unrecognised is kept word for word, so no file is refused.

Press Import .py, paste a program, or drop a file anywhere on the page.

The block set goes from 26 to 95 across eight categories: lists, custom
blocks and a Python category join the original five, and the existing ones
fill out with the operators, text handling and control blocks the desktop
app has. Everything still runs in the page.

Six programs are tested three ways: run by real Python, imported into blocks
and run by the demo's interpreter, then turned back into Python and run
again. All three agree exactly, which turned up four real faults on the way:
numeric slots trimming the text they were given, print with three or more
arguments falling back to raw code, list literals never reaching the
interpreter, and len() of a plain variable doing the same.

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

Author: ZDStudios

README.md

@@ -33,10 +33,11 @@ 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.
+[`index.html`](index.html) is a standalone version of the same idea: one file, no
+dependencies, no build step. 95 blocks, drag and snap, the Python appearing live
+beside you, Run working right there in the page — and you can **drop a `.py` file
+on it** and watch the whole program turn into blocks. The desktop app adds pip,
+virtual environments, files, the web blocks and the MCP server.
 
 ---
 
@@ -346,23 +347,42 @@ finally runs the generated example program and checks its output.
 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
+It shares the desktop app's ideas in about 3,400 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
+* **95 blocks** across eight categories — 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
+* **it reads Python too** — see below
 
 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.
+### Import a Python file, in the browser
+
+Press **Import .py**, paste a program, or just drop a `.py` file onto the page.
+A small tokeniser and recursive-descent parser — written from scratch in
+JavaScript, since browsers have no `ast` module — reads the file and builds the
+blocks.
+
+It understands assignments, `if`/`elif`/`else`, `while`, `for` over `range` and
+over lists, `def` with parameters and returns, `break`, `continue`, f-strings,
+comparisons, `and`/`or`/`not`, list and string methods, and the usual built-ins.
+Functions become real **custom blocks** with their own define hat and call block.
+Anything it does not recognise is kept word for word in a "python" block, so no
+file is ever refused.
+
+> Six programs were tested three ways: run by real Python, imported into blocks
+> and run by the demo's own interpreter, then turned back into Python and run
+> again. All three produce **identical output** every time.
+
+What the demo leaves out: pip, virtual environments, files, the web blocks and
+the MCP server. Those need a machine, not a tab — they are in the desktop app.
 
 ---