React Starter
This example shows a smiling face built entirely with React, rendered as SVG shapes that scale to fill the browser window. It uses React 16.9 and ReactDOM to create and mount a component tree, with circles positioned via the `transform` attribute for the face, eyes, and mouth. All dimensions—like `centerX`, `eyeOffset`, and `strokeWidth`—are derived from `window.innerWidth` and `window.innerHeight`. The code demonstrates declarative SVG rendering within React’s virtual DOM, using numeric props for geometry and a `<g>` element to center the composition.