Twelve pastel circles in a fixed layout demonstrate a straightforward data binding workflow with D3. Each circle’s position and radius are predefined in an array, and D3 selects all `circle` elements, binds the data, and appends new circles with the `enter` selection. The SVG renders with rounded corners and a subtle shadow from CSS. The example uses `d3.select` and `selection.attr` to apply the `cx`, `cy`, `r`, and `fill` attributes, mapping each data object to a visually distinct geometric shape.