A blank SVG canvas fills the browser window, with a single large rounded rectangle drawn across its entire dimensions. The example demonstrates the minimal setup required to create a D3 visualization, using `d3.select` to target the SVG element and setting its width and height attributes based on `document.body.clientWidth` and `document.body.clientHeight`. The rectangle is appended with a 40-pixel corner radius, styled by an external Ubuntu font and hidden overflow CSS. No data or interactive behavior is present, serving purely as an empty starting point.