This example uses D3.js (v5) and SVG to render three concentric rings of colored squares, each labeled with a number. The code constructs a custom `Square` class and uses `d3.select`, `selectAll`, and data joins to append rectangles and text elements within an SVG viewBox. Square positions are calculated using trigonometry with varying radii for each ring, though the sample data and color definitions are only partially implemented in the provided files.