Hello world
This example renders a simple, yellow smiley face as an SVG graphic using React and D3. It constructs the face from primitive shapes: two circles for the eyes and an arc path for the mouth, all positioned relative to the center of a 960x500 viewport. The code defines the mouth with `d3.arc()`, specifying inner and outer radii, as well as start and end angles, while React components generate the SVG elements. The rendering is static, with no data loading or user interaction.