A yellow smiley face is rendered across the full browser window using React and D3 v7. The face consists of SVG circles for the head and eyes, and a D3 arc path for the mouth, all positioned relative to the center of the viewport. The example demonstrates how to integrate React components with D3's arc generator to create geometric shapes. The code imports React and uses ReactDOM to mount the SVG, while D3's `arc()` calculates the mouth's curved path with specific start and end angles.