An interactive fractal tree of circles responds to mouse position, with cursor X controlling recursion depth and Y controlling branch angle. The SVG is rendered using D3 v4’s data join, where each node is drawn as a circle whose radius shrinks by a fixed scale factor per level. The fractal recursively branches when the depth modulo 11 equals zero, flipping the angle sign to create alternating asymmetry. The code uses `svg.selectAll("circle").data()`, `.enter()`, and `.exit().remove()` to update the visualization live on every `mousemove` event.