v2: full rewrite in React/Node.js - real-time audio-reactive visualizer with HALO, AURA and BARS modes, Spotify OAuth, Web Audio API mic sync

Author: rmfranken

.gitignore

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+.env
+node_modules/
+.venv-bg/

README.md

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+# Spotify Viber
+
+A premium, fullscreen Spotify Web Visualizer that reacts to live audio using the Web Audio API and the device's microphone/system loopback.
+
+## Features
+
+- **Spotify OAuth Integration**: Authenticates with Spotify to fetch and display the currently playing track's artwork, song name, and artist.
+- **Ultra-Low Latency Audio Sync**: Bypasses rate-limited Web APIs by using the browser's native `AnalyserNode` to perform Fast Fourier Transforms (FFT) on your microphone or system audio feed, achieving near instant 0-latency synchronization.
+- **Dynamic Visualizer Modes**:
+  - `HALO`: 3 overlapping layers of flowing Bezier curves mapped to polar coordinates around the album art.
+  - `AURA`: A screen-filling, radial light gradient that pulses and morphs like a lava lamp.
+  - `BARS`: A classic neon 64-band equalizer running across the bottom of the screen.
+
+## Project Structure
+
+- `frontend/`: The React+Vite frontend where all the visualization and Spotify player UI lives.
+- `server.js`: A minimalistic Node.js Express server to handle Spotify OAuth callbacks, token exchange, and environment variables without exposing secrets to the browser.
+
+## Installation & Setup
+
+1. Setup Spotify Developer Credentials
+    - Go to your [Spotify Developer Dashboard](https://developer.spotify.com/dashboard/).
+    - Create an App and get your `Client ID` and `Client Secret`.
+    - Set your Redirect URI to `http://127.0.0.1:8888/callback` (must be `127.0.0.1`, not `localhost`).
+
+2. Create a `.env` file in the root directory:
+    ```env
+    SPOTIPY_CLIENT_ID=your_client_id
+    SPOTIPY_CLIENT_SECRET=your_client_secret
+    SPOTIPY_REDIRECT_URI=http://127.0.0.1:8888/callback
+    ```
+
+3. Install dependencies:
+    ```bash
+    npm install
+    cd frontend && npm install
+    ```
+
+4. Run the full stack (backend Auth server + Vite development preview):
+    ```bash
+    npm run dev
+    ```

frontend/.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?

frontend/README.md

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+# React + Vite
+
+This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.
+
+Currently, two official plugins are available:
+
+- [@vitejs/plugin-react](https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react/README.md) uses [Babel](https://babeljs.io/) for Fast Refresh
+- [@vitejs/plugin-react-swc](https://github.com/vitejs/vite-plugin-react-swc) uses [SWC](https://swc.rs/) for Fast Refresh

frontend/eslint.config.js

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+import js from '@eslint/js'
+import globals from 'globals'
+import react from 'eslint-plugin-react'
+import reactHooks from 'eslint-plugin-react-hooks'
+import reactRefresh from 'eslint-plugin-react-refresh'
+
+export default [
+  { ignores: ['dist'] },
+  {
+    files: ['**/*.{js,jsx}'],
+    languageOptions: {
+      ecmaVersion: 2020,
+      globals: globals.browser,
+      parserOptions: {
+        ecmaVersion: 'latest',
+        ecmaFeatures: { jsx: true },
+        sourceType: 'module',
+      },
+    },
+    settings: { react: { version: '18.3' } },
+    plugins: {
+      react,
+      'react-hooks': reactHooks,
+      'react-refresh': reactRefresh,
+    },
+    rules: {
+      ...js.configs.recommended.rules,
+      ...react.configs.recommended.rules,
+      ...react.configs['jsx-runtime'].rules,
+      ...reactHooks.configs.recommended.rules,
+      'react/jsx-no-target-blank': 'off',
+      'react-refresh/only-export-components': [
+        'warn',
+        { allowConstantExport: true },
+      ],
+    },
+  },
+]

frontend/index.html

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+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Vite + React</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.jsx"></script>
+  </body>
+</html>