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+# WebAssembly Code Explorer
+
+A browser-based tool for visually exploring WebAssembly (`.wasm`) binary files. It presents a synchronized **hex dump** and **disassembly view** side by side, with color-coded sections and bidirectional click-to-highlight navigation.
+
+![WebAssembly Code Explorer](./bug1154731b.png)
+
+---
+
+## Features
+
+- 📂 **Open any `.wasm` file** directly from your local machine
+- 🎨 **Color-coded hex dump** — each byte group is colored by its WebAssembly section type (functions, exports, imports, operators, etc.)
+- 🔗 **Bidirectional navigation** — click a byte in the hex view to highlight the corresponding instruction, and vice versa
+- 📝 **Disassembly panel** — full WAT (WebAssembly Text Format) disassembly with byte offsets
+- 🗺️ **Source map support** — load a source map alongside your `.wasm` file to see the original source lines (C, Rust, etc.)
+- 🏷️ **Hover annotations** — hover over any byte group to see detailed info: section type, operator name, function signatures, import/export details, and more
+- 🚀 **PostMessage API** — can be embedded in other tools and driven via `window.postMessage`
+
+---
+
+## Getting Started
+
+No build step or package installation required. The project runs entirely in the browser.
+
+### Run locally
+
+```bash
+# Clone the repository
+git clone https://github.com/<owner>/wasmcodeexplorer.git
+cd wasmcodeexplorer
+
+# Serve with any static file server
+npx serve .
+# or
+python3 -m http.server 8080
+```
+
+Then open `http://localhost:8080` in your browser.
+
+> ⚠️ You must use a local server — opening `index.html` directly as a `file://` URL will fail due to browser CORS restrictions on module loading.
+
+### Usage
+
+1. Click **Open File** and select a `.wasm` binary
+2. The left panel shows the **hex dump** with color-coded byte groups
+3. The right panel shows the **disassembly** (WAT format)
+4. Click any byte group or instruction to highlight the corresponding element in the other panel
+5. Hover over byte groups to see annotations (section type, operator details, etc.)
+
+#### Loading a source map
+
+To see original source lines alongside the disassembly:
+- Click **Open File** again after loading a `.wasm` file
+- Select the corresponding `.map` or source file
+
+#### PostMessage API
+
+The explorer can be embedded in an iframe and controlled programmatically:
+
+```
+# Open the explorer with the postmessage API enabled
+http://localhost:8080?api=postmessage
+
+# Send a wasm buffer to load
+window.postMessage({ type: "wasmexplorer-load", data: { buffer: wasmBuffer } }, "*")
+
+# Listen for the ready event
+window.addEventListener("message", (e) => {
+  if (e.data.type === "wasmexplorer-ready") { ... }
+})
+```
+
+---
+
+## Project Structure
+
+```
+wasmcodeexplorer/
+├── index.html            # Main HTML — toolbar, hex dump panel, disassembly panel
+├── viewer.js             # Core logic — wasm parsing, color mapping, hex rendering, click events
+├── source-map-utils.js   # Source map parsing and display logic
+├── heap.js               # Min-heap data structure (used internally by source map utils)
+├── style.css             # Stylesheet
+├── helloworld2.wasm      # Sample .wasm file for quick testing
+└── LICENSE               # MPL-2.0
+```
+
+---
+
+## Dependencies
+
+Loaded via CDN — no `npm install` needed:
+
+| Package | Purpose |
+|---|---|
+| [`wasmparser`](https://www.npmjs.com/package/wasmparser) | Parses `.wasm` binary format |
+| [`wasmdis`](https://www.npmjs.com/package/wasmparser) | Disassembles wasm to WAT text format |
+| [SystemJS](https://github.com/systemjs/systemjs) | Module loader |
+
+---
+
+## Color Reference
+
+The hex dump uses these colors to distinguish wasm sections:
+
+| Color | Section Type |
+|---|---|
+| Color 1 | Section header (`BEGIN_SECTION`) |
+| Color 2 | Code operators / init expressions |
+| Color 3 | Function body start / reloc section header |
+| Color 4 | Wasm file header (`BEGIN_WASM`) |
+| Color 5 | Exports, imports, type entries, function entries |
+| Color 6 | Globals, memory, data, tables, elements |
+| Color 7 | Name section entries, reloc entries |
+
+---
+
+## Contributing
+
+Contributions are welcome! Here's how to get started:
+
+1. Fork the repository
+2. Create a new branch: `git checkout -b my-feature`
+3. Make your changes
+4. Open a Pull Request with a clear description of what you changed and why
+
+### Areas open for contribution
+
+- Fix the known scroll-sync bug (see `bug1154731b.png` and the `FIXME` comments in `viewer.js` and `source-map-utils.js`)
+- Add support for newer WebAssembly proposals (SIMD, threads, etc.)
+- Improve mobile/responsive layout
+- Add more test `.wasm` sample files
+- Modernize the module system (migrate from SystemJS to native ES modules)
+- Improve annotation coverage for more section types
+
+---
+
+## License
+
+[Mozilla Public License 2.0](./LICENSE)