This example renders a full-screen SVG smiley face using React components for the face, eyes, and mouth. The face is drawn as a yellow circle with a black stroke, while the eyes are simple offset circles. The mouth is created with the d3.arc() API, producing a semicircular path by calculating inner and outer radii with specific start and end angles. All shapes are positioned relative to the center of the viewport using the d3.js v7 library and React DOM for rendering.