This example shows a yellow smiley face rendered across the full browser window, with two black eyes and a downward-curving mouth drawn as an arc. The face is built using React components that render SVG elements, including circles for the head and eyes and a path for the mouth. The mouth path is generated with the `d3.arc` function, specifying inner and outer radii and start and end angles. The visualization uses React 16.9.0, ReactDOM, and D3 v7.3.0, with the root SVG centered in the viewport.