A smiley face is rendered as a full-screen SVG, with its size and position derived from the browser window dimensions. The face is composed of three React components: a yellow background circle, two eyes, and a mouth drawn using D3’s `arc` generator. The code uses React 16.9 for component structure, D3 v6 for arc calculations, and SVG for all visual output, with dimensions and offsets defined as constants in the main `App` component.