This example displays a full-screen smiley face built with React and D3 v7, centered on the viewport. It shows a yellow circle with black stroke, two eye circles, and a mouth arc drawn using the D3 `arc` generator with specified angles. The SVG rendering uses React components to create the shapes, with dimensions calculated from `window.innerWidth` and `window.innerHeight`. The code defines constants for eye offsets, eye radius, and mouth geometry, rendering everything dynamically to fit the browser window.