This example shows a React application with a fixed left-side navigation menu that stays in place while the page scrolls. The code uses React’s `createRoot` from `react-dom` to render a simple app with a `SideNav` component, which contains links to page sections. The navigation’s styling is defined in a separate CSS file, setting a dark background, fixed width, and full height. The main content area is shifted right with an inline `marginLeft` style to accommodate the sidebar, demonstrating a basic layout pattern with no additional data or interactive behavior beyond the static links.