Fifteen circles, arranged in a sine-wave pattern across the viewport, demonstrate basic D3 data joins and selections. The example uses D3 v6's `select`, `range`, and `selectAll().data().enter().append()` to bind an array of numbers to SVG circle elements, positioning them with `cx` and `cy` attributes. Rendered as an SVG in a full-window `<svg>` element, it shows how D3's functional attribute syntax derives coordinates from the bound data. The circles are static, with no interactions or transitions.