Smiley Face Part I
A yellow smiley face rendered with SVG circles for the head and eyes, plus a D3 arc path for the mouth, is drawn centered on a 960×500 canvas. The React component uses JSX to position elements via the `arc()` generator from `d3`, with the mouth’s inner radius and angles defining its half-open shape. Eye placement and stroke width are computed from offset constants, while the head circle’s radius derives from the viewport height. The code imports `arc` from `d3` and leverages React 16 and D3 v5 for declarative SVG rendering.