This example demonstrates the minimal setup for a D3.js visualization within an HTML page, rendering a single red SVG square. It uses React as the framework, with D3 v6 loaded via CDN. The code selects the SVG element with `d3.select`, applies a background color, and links an external stylesheet for heading formatting. It’s a bare-bones starter template showing how to combine core web technologies—HTML, CSS, and JavaScript—for SVG-based graphics.