A lone circle fills a 960-by-500 SVG canvas, demonstrating how a single SVG `<circle>` element with a large radius (`r="400"`) is styled entirely through an external CSS file. The example shows the interplay between SVG geometry and CSS styling rules, with the circle’s fill, stroke, or other visual properties defined in `style.css` rather than inline attributes. This minimal setup highlights how CSS can control SVG presentation, using the browser’s native SVG rendering support without any JavaScript libraries. The code relies solely on standard SVG markup and CSS, making it a pure HTML/CSS demonstration.