Twenty colored circles are rendered in an SVG, where each circle can be either clicked or dragged. A click triggers a two-step radius animation (expanding to 64, then shrinking back to 32), while dragging moves the circle and, once the drag exceeds a small threshold, brings the circle to the front using `raise()` and adds an active class. The example uses D3 v4’s `d3.drag()` with `.clickDistance(4)` to distinguish clicks from drags, alongside manual checks on `sourceEvent` coordinates to handle edge cases where the drag ends near the start point. Data is generated randomly as an array of 20 `{x, y}` objects, with colors assigned via `d3.scaleOrdinal` and `d3.schemeCategory20`.