Fork of Circles with D3
A dynamic SVG canvas displays seven multicolored circles with varying radii and opacity, positioned at explicit coordinates. The D3.js code uses the `select` and `join` API to create and update the SVG element and its circle children via method chaining. Circle properties like `cx`, `cy`, `r`, `fill`, and `opacity` are bound directly to data objects, demonstrating D3’s data-binding and General Update Pattern.