A blank, full-viewport SVG canvas renders as a large rounded rectangle, filling the entire browser window. The visualization uses d3 v6’s `select` to target the empty `svg` element and sets its width and height to the viewport dimensions via `clientWidth` and `clientHeight`. A single `rect` is appended with a 40-pixel corner radius, creating a soft-edged frame. The CSS fixes the body position to eliminate scrolling, ensuring the canvas remains static and unobstructed, with no data or interaction yet defined.