A black rounded rectangle fills the entire browser window, creating a stark, minimalist blank canvas. The visualization uses D3 v5’s `select` method to target the SVG element, then sets its width and height to match the viewport dimensions. It appends a single `rect` with rounded corners (`rx`) and a black fill via CSS. The code dynamically reads `document.body.clientWidth` and `clientHeight` to size the graphic responsively, demonstrating a simple SVG rendering approach with no data or interaction.