This example demonstrates the simplest possible D3 v7 setup: a single circle rendered in an SVG. The code uses `d3.select` to target the SVG element and appends a circle with a fixed radius of 200 pixels. The HTML page loads D3 from a CDN, styles the body with a massive 13em font size, and relies on an external `bundle.js` for the JavaScript. It serves as a minimal starting point for D3 development, showing only the core selection and manipulation pattern without any data binding or interaction.