This example shows a yellow smiley face drawn with SVG, centered in a 960-by-500 viewport. The face consists of three circles for the head and eyes, plus an arc for the mouth, all rendered using React components. The code uses React 16.9 and D3 v5, specifically the `arc` generator from `d3` to create the mouth path. Coordinates are computed from fixed constants and a centered group transform, with the head circle radius derived from the viewport height.