This example shows a simple smiley face built with React and D3, rendered as SVG. It draws a yellow circle with a black stroke, two eyes, and a curved mouth using the `d3.arc()` generator. The face is centered via a `<g>` transform, with eye and mouth positions computed from offset constants. The code uses React 16.9 for DOM rendering and D3 v5 for the arc path calculation, with all shapes drawn declaratively as SVG elements.