This example shows a smiley face rendered as a full-screen SVG using React. It demonstrates how to compute geometric properties, such as the face radius and eye positions, based on the browser window dimensions. The app is built with React and ReactDOM, and uses pure SVG elements like `<circle>` and `<g>` for drawing, with all styling and transformations applied inline. No external data is loaded; the visualization is purely generated from hardcoded constants for eyes, mouth, and stroke width.