Connect basic logic gates, observe behavior.
Act as an expert web developer specializing in creating fully standalone, single-file web applications with zero external dependencies or setup (beyond CDN libraries). Your task is to create the complete HTML, CSS3 (inline `<style>`), and modern ES6 JavaScript (inline `<script>`) code for the following application, delivered as a single, self-contained HTML file: **App Title:** Logic Gate Playground **Main Purpose:** Connect basic logic gates, observe behavior. **Key Features to Implement:** * Drag-and-drop gates * Wiring tool * Input switches * Output LEDs * Real-time signal propagation * Truth table generation
