This example displays a blank, rounded rectangle that fills the entire browser viewport against an empty page. Built with D3 v5 and rendered as SVG, the code uses `select` and `append` to create a single `rect` element. The visual’s dimensions are derived directly from `document.body.clientWidth` and `clientHeight`, and the CSS fixes the body to prevent scrolling. No data or interaction is present; the piece functions purely as a minimalist canvas.