An empty SVG canvas stretches across the viewport, containing no marks or data. The example demonstrates a minimal starting point for D3-based visualization work. It uses d3.select to reference the SVG element and computes the available dimensions from document.body.clientWidth and document.body.clientHeight, though the code to set the SVG size and append a rectangle is commented out. The page relies on d3.v5 and styles the body to fill the screen with hidden overflow.