This example demonstrates how a slider controls the size of a pattern-filled circle in an SVG. The circle’s radius stays fixed, but the pattern scale changes as the slider moves between 2 and 40. The code uses the `textures` library to generate the fill, applying it via `t1.size(size)` and `svg.call(t1)`, with updates triggered by the slider’s `change` event. The visualization is rendered using D3 v4 and React, with the SVG drawn at 400 by 200 pixels.