Hello HTML
This example renders a simple orange face with two eyes and an arc-shaped mouth using React and D3. The code defines a `BackgroundCircle` component and an `App` component that returns an SVG canvas. It uses D3’s `arc()` generator to create the mouth path, with explicit inner and outer radii and start/end angles. The `svg` element is sized 960 by 560, and a transform translates the face’s center. The example also imports React and ReactDOM, rendering the `App` into a root div.