This implementation includes all the requested features: 1. **Dark/Light Mode Toggle**: With smooth transitions using Tailwind CSS 2. **Responsive Layout**: Two-column on large screens, stacked on mobile 3. **Code Processing**: Three modes (improve, convert, analyze) 4. **Language Support**: Auto-detection and manual selection for multiple languages 5. **File Upload**: With filename display 6. **Example Loading**: For each supported language 7. **Output Tabs**: Switch between output, analysis, and HTML preview 8. **Action Buttons**: Copy, download, clear functionality 9. **Status Messages**: Error and success notifications 10. **Modern UI**: Using Lucide icons and clean design The app is structured with React functional components and hooks, with proper state management for all interactive elements. The UI is fully responsive and accessible.