A blank, rounded rectangle fills the entire browser viewport, serving as a minimal canvas with no data or marks rendered. The SVG element is dynamically sized to match the window dimensions using the D3v5 `select` API, and a single `rect` is appended with a 40-pixel corner radius. The complete visual result is a simple, frameless field, demonstrating basic SVG construction with D3’s selection and attribute-chaining methods against a fixed-position, full-screen body.