SVG fundamentals
This example demonstrates the fundamental building blocks of SVG rendering with D3.js, creating 15 circles positioned across the screen using a sine wave pattern. The code imports `select` and `range` from d3, appends an SVG element to the body sized to the full window, and uses the data join pattern with `selectAll`, `data`, and `enter` to create circles. Each circle receives a fixed radius of 20 pixels, with horizontal positions computed as multiples of 50 and vertical positions determined by the sine function. The visualization serves as a minimal, self-contained introduction to creating SVG shapes with D3's data-binding approach.