A blank, rounded rectangle fills the entire 960 by 500 pixel SVG canvas, demonstrating a minimal starting point for visualization projects. The example uses D3 v5’s `select` method to target the SVG element and set its dimensions, then appends a single `rect` with a 40-pixel corner radius. The accompanying CSS fixes the body to the viewport edges and hides overflow, ensuring the canvas occupies the full screen without scrollbars. This serves as a template for building more complex D3-based graphics.