Smiley Face Part I
This example uses React and D3 to render a simple SVG smiley face. The React component computes coordinates for a yellow circle face, two black eyes, and a mouth using constant variables for width, height, and offsets. The SVG output is drawn with a yellow fill, black stroke, and a fixed stroke width. The code uses the ReactDOM `render` method to mount the component into the HTML root element, with D3 loaded but not directly used in the visible logic.