A smiling face rendered with SVG uses React components for each facial feature, including a gradient-filled face, eyes with colored irises and pupils, a mouth built from D3 arcs, and teeth as rectangles. Eyebrows are separate React elements with CSS hover effects that change their fill and stroke via custom properties. The face rotates slightly, and the eyebrows animate upward using SVG's built-in `<animate>` element with keyTimes and repeatCount, while the entire scene sits on a green background gradient.