This example demonstrates a minimal D3.js setup within an HTML page, where circles, groups, and rectangles respond to interactions and data binding. It shows how to use D3 v7 selections to manipulate SVG attributes, such as toggling circle fill colors on click and generating random radii. The code uses `d3.selectAll`, `attr`, `style`, and the data join pattern with `join('rect')` to render pink rectangles from a static array. Text labels are appended to group elements, and the page relies on the d3-selection-multi plugin for the `attrs` method.