This example shows a stylized smiley face built with React and D3 v5, rendered as an SVG. It uses a radial gradient for the background and a rotated linear gradient for the face fill. The eyes, pupils, and eyebrows are separate React components, with the eyebrows styled using CSS variables that change their fill and stroke-width on hover. The mouth is drawn with D3’s `arc` generator, and a blue tongue is rendered as a separate path. The code defines layout constants for positioning all facial features.