This example shows a classic yellow smiley face rendered as a reusable React component using D3’s `arc` generator to draw the mouth as a path. The face consists of SVG circles for the head and eyes, with a black stroke for the face outline, all positioned via absolute coordinates derived from the viewport dimensions. The code imports `React` and `ReactDOM` to manage rendering, while `d3.arc` computes the mouth’s arc geometry between fixed start and end angles. The component returns a single `<svg>` element, and React mounts it into the DOM root.