This example demonstrates a basic tooltip interaction on an SVG circle, showing how D3.js can handle mouse events to reveal hidden information. A single teal circle is rendered in the center of an SVG canvas, and hovering over it displays a text label that follows the cursor’s movement. The implementation uses D3 v4 selections with `.on()` for mouseover, mousemove, and mouseout listeners, while the tooltip itself is an SVG text element toggled via style visibility properties. The circle’s fixed position and the tooltip’s offset calculations are hardcoded in the script.