This example draws a single circle in an SVG using D3.js v5. The circle is appended to the root `<svg>` element and positioned with hard-coded values for its center and radius, using the `select` and `append` APIs. The circle’s radius is set to half the SVG’s height, and its x- and y-coordinates are both set to half the SVG’s height, resulting in a face-like shape centered vertically. The page loads D3 from an unpkg CDN and includes minimal CSS that hides overflow.