A nearly empty SVG canvas fills the entire browser viewport, containing only a single small rectangle with default black fill. The example demonstrates the most basic D3 setup: selecting the root `<svg>` element, reading the browser window’s dimensions, and setting the SVG’s width and height attributes accordingly. Using d3.select, the code appends one `<rect>` element with hardcoded width and height values, serving as a minimal starting point for further visualization development. The renderer is SVG with D3 v5, and the layout is fully responsive to the viewport size.