This example displays a set of seven semi-transparent circles, each with a unique color and varying size, arranged across a pale green background. The visualization uses D3 v7’s selection and data-join methods to bind an array of hardcoded position and radius values to SVG circle elements. The `viz` function creates an SVG canvas sized to the container and renders each circle with specified `cx`, `cy`, `r`, and `fill` attributes, while a fixed opacity of 0.7 gives the shapes a layered appearance.