A blank, rounded rectangle fills the browser viewport, sized to the full window and created with a single `rect` element appended to an SVG. The visualization uses D3 v7's `select` method to target the SVG and set its width and height attributes dynamically based on `document.body.clientWidth` and `clientHeight`. The example demonstrates a minimal SVG setup within an HTML page, styled by CSS to remove margins and hide overflow, with a placeholder ES6 module exporting a string.