Build simple DC circuits, visualize voltage/current.
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:** Basic Circuit Simulator (DC) **Main Purpose:** Build simple DC circuits, visualize voltage/current. **Key Features to Implement:** * Drag-and-drop components * Set values * Calculate/display voltage/current * Visual current flow
