Hello HTML
This example shows a yellow smiley face rendered as an SVG using React and D3. It draws a yellow circle for the face, two black circles for the eyes, and a D3 `arc` path for the mouth. The component uses `ReactDOM.render` to inject the SVG into the HTML root. The `arc` API defines the mouth’s inner and outer radii and angular range, producing a half-circle that opens downward. Rendering is vector-based with fixed pixel dimensions for the 960-by-500 viewport.