A minimal React application renders a gray SVG canvas with a small black circle that follows the mouse cursor. The code uses React's `useState` and `useCallback` hooks to track cursor position and update the circle's `cx` and `cy` attributes. It imports `Eyes` and `Mouth` components, which draw placeholder facial features using SVG circles and a D3 `arc` path, though these are not currently instantiated in the main `App` component. The example demonstrates basic React event handling and SVG rendering within an HTML page.