This example renders a smiling face using React and D3, drawing a yellow circle with two eyes and a mouth arc that scales to the browser window. The SVG output uses React components for circles and a D3 `arc()` generator to create the mouth path. Dimensions such as eye offset, radius, and stroke width are defined as constants, while the face is centered using a translation transform. The visualization relies on React 16.9 and D3 v5, with the SVG adjusting dynamically to viewport size.