This example displays a large, full-screen smiley face rendered as an SVG in React. The face fills the viewport, with a radial gradient from gold to red, black eyes positioned symmetrically, and a mouth formed by a D3 arc path. The code leverages ReactDOM to mount the component and uses D3’s `arc` generator to define the mouth’s shape based on radius and angle calculations, while circles handle the face and eyes, and a line adds a nose.