This example demonstrates how SVG shapes can be styled using CSS within a D3.js visualization. It renders a single, empty SVG element with a fixed width and height, whose background color is set to red via D3’s selection and style method. The page also applies global CSS rules to remove margins and hide scrollbars, ensuring the SVG fills the viewport without distraction. The code relies on D3 v5 for DOM selection and styling, while the overall structure uses standard HTML and CSS.