A blank SVG canvas fills the browser window, rendered as a single rounded rectangle that adapts to the viewport dimensions. The example demonstrates a minimal D3 setup where `d3.select` attaches to the `svg` element, and the viewport size is read from `document.body.clientWidth` and `document.body.clientHeight`. Using d3.v5, the code appends a `rect` with a 40-pixel corner radius, while the CSS hides any page overflow. No data or interactive behavior is present; the piece simply shows the initial scaffolding for a charting project.