A blank, rounded rectangle fills the entire browser viewport, offering an empty visual canvas. The example demonstrates the minimal setup for a D3.js v5 visualization using SVG rendering, where the page dimensions are read directly from the document body and applied to the SVG element. The code relies on d3.select to target the pre-existing svg tag and appends a single rect with corner radius. No data drives the display; the focus is purely on establishing a flexible, full-window drawing surface.