A blank, rounded rectangle initially fills the browser viewport. The visualization demonstrates a minimal setup for a scalable vector graphics (SVG) canvas, dynamically sizing its dimensions to match the full browser window. The code constructs the empty canvas using the ‘select’ function from the D3 library, which is used to query the SVG element and append the background rectangle. Styling is applied via CSS to fix the body’s position and remove margins, ensuring the canvas remains edge-to-edge. No data or interaction is present; it serves as a starting point for further charting.