This example shows a smiley face built from modular React components, with a yellow circular face, two black radial-gradient eyes, and a curved mouth arc. It demonstrates splitting D3-based SVG rendering into separate ES6 module files, using React fragments in the eyes component and a shared face container for positioning. The code uses React 16.9, D3 v5’s `arc()` API for the mouth path, and renders everything into an SVG via `ReactDOM.render`. All geometry values are defined as constants in the main `index.js` file.