A blank SVG canvas fills the browser window, displaying a single rounded rectangle that spans the entire viewport. The example demonstrates a minimal setup for an interactive visualization framework, using D3 v5 to select the SVG element and set its dimensions based on the current window size. The code relies on `d3.select` and the SVG `rect` element with rounded corners (`rx`), while the fixed-position body styling prevents scrolling. No data or interaction is implemented, serving as a starting point for further development.