This example renders a simple smiley face in SVG using React and D3. The face is composed of a yellow background circle, two black eye circles, and a mouth path generated with the `arc()` function from D3. The code uses React to create the SVG elements and computes coordinates with static variables, such as `eyeOffsetX` and `eyeOffsetY`. The mouth arc is drawn with an inner and outer radius, starting and ending angles defining a half-circle shape. The visualization shows basic composition and DOM manipulation with React 17 and D3 v7.