This example shows a smiley face rendered as a yellow circle with two black eyes and a curved mouth, all centered in an SVG canvas. The face is built using React components that calculate positions and dimensions from constants, while D3’s `arc()` generator creates the mouth’s path. React handles DOM updates, and D3 v5 provides the geometric shape calculation. The stroke, eye, and mouth radii are defined as variables, demonstrating a modular, parameterized approach to combining React’s declarative UI with D3’s drawing utilities.