Blank Canvas
A blank SVG canvas fills the browser window, defined by a single rounded rectangle that matches the viewport dimensions. The page appears as an empty, frameless space with no data or interaction, emphasizing the starting point for a visualization. The code uses D3 v5’s `select` and `arc` imports, though only `select` renders the static shape. The SVG size adapts to the document body’s client height and width, while CSS fixes the body and hides overflow, ensuring the canvas remains fully visible without scrollbars.