A full-screen SVG rectangle stretches to the browser window’s dimensions, its corners rounded by an rx attribute. The canvas remains otherwise blank, an empty visual field defined solely by the viewport’s width and height. Built with the v5 version of D3, the code uses `select` to target the SVG element and `attr` to set its size and the rectangle’s rounded geometry. No data is loaded, and no interaction or animation occurs, leaving the example as a minimalist exploration of spatial boundaries.