This example demonstrates a minimal tooltip interaction in D3.js, showing how a simple text label appears and follows the mouse cursor when hovering over a circle. The code uses D3 v5 to append a hidden div as the tooltip and positions it dynamically on mouse events. It employs `mouseover`, `mousemove`, and `mouseout` handlers to control visibility and track the pointer coordinates via `event.pageY` and `event.pageX`. The circle is drawn with an SVG `circle` element, styled with a black stroke and aliceblue fill, inside a 300-by-300-pixel SVG container.