A grid of randomly generated smiley faces appears, each rendered as a yellow circle with a black stroke, two eyes, and a d3-arc mouth. The demo shows how React components compose a parameterized SVG face, with each face receiving randomized values for stroke width, eye offset, eye radius, and mouth dimensions. Built with React and D3 v7, the code constructs each face using a `FaceContainer` and `arc()` from D3, while the `App` component maps over a range to produce 18 unique faces.