This example shows a single gray circle centered in an SVG canvas, rendered using React and D3 v7. The circle is positioned statically at the midpoint of the 960×500 viewport, with no interactive data binding. It demonstrates React’s `ReactDOM.render` method to mount a functional component that returns an SVG `<circle>`, while a separate static SVG in the HTML displays two additional unfilled circles. A mouse move handler logs events to the console, but no visual feedback occurs. The rendering relies on React’s virtual DOM and D3’s SVG utilities.