This example presents an initially blank, full-viewport canvas. It displays a single, fixed, rounded rectangle that fills the entire browser window. The visualization is rendered using an SVG element, whose dimensions are set to match the document body’s width and height via the D3.js library. The code imports the `select` function from D3 and uses it to configure the SVG, appending a rectangle with rounded corners. The underlying styles, defined in CSS, fix the body to the viewport, ensuring the blank canvas remains the sole focus of the page.