A yellow circle with a black outline and two black eyes forms a sad face. The mouth is drawn as an arc using the `d3.arc` API, with its inner and outer radii set via `d3.arc()` and a path element. The face is built with React components rendering SVG elements, including circles for the background and eyes. The `arcCenterX` and `arcCenterY` variables position the mouth separately from the face’s center, while the stroke width is defined as a constant.