A yellow circle follows the mouse cursor across an SVG canvas, updating its position in real time. The React application uses the `useState` and `useCallback` hooks to track mouse coordinates from the `onMouseMove` event, then renders a single `<circle>` element whose `cx` and `cy` attributes are bound to that state. The circle starts at the canvas center and moves smoothly as the user moves the pointer, with the SVG viewport set to 960 by 500 pixels.