This example demonstrates a blank, interactive-free canvas that fills the browser viewport with a single rounded rectangle. Using the D3.js library’s `select` function, it dynamically retrieves the body’s client width and height, then sets the SVG’s dimensions accordingly and appends a `rect` element whose corners are rounded via the `rx` attribute. The visualization relies on D3 v5 and SVG rendering, with styling provided by a fixed-position CSS layout that ensures the canvas remains fully visible.