A single large circle sits at the center of an SVG canvas, rendered with a thick black outline and no fill. The example demonstrates basic D3 shape creation and attribute manipulation, using `d3.select` to target the SVG element and `circle.attr` to set the circle's radius to 200 and horizontal position to half the viewport width (960/2). The code imports only the `select` function from D3 v6, leaving the vertical position at its default, and the page styling removes margins and hides overflow for a clean, full-window display.