An empty SVG canvas fills the browser window, displaying only a rounded rectangle that spans the full viewport. The example demonstrates the minimal setup required to render a blank visualization surface. The code uses D3 v5's `select` and `arc` imports to create an SVG container, then appends a `<rect>` element with its width and height set to the document body's client dimensions. The CSS fixes the body to prevent scrolling, ensuring the canvas remains static.