This example renders a full-screen smiley face using React and D3 v7, with SVG elements positioned relative to the window’s center. It draws a yellow circle for the head, two black eyes, and a mouth arc created via `d3.arc()` with fixed inner and outer radii. The React component manages the SVG structure, while D3 computes the mouth’s path. The code resizes dynamically by using `window.innerWidth` and `window.innerHeight` for the viewport dimensions. No interactive behavior is implemented; the visualization is static.