Circles with D3
Six translucent circles in contrasting colors—gold, pink, cyan, purple, green, and magenta—overlap on a pale green background. Each circle’s position, radius, and fill are hard-coded in an array of objects. The example uses D3 v7’s `select`, `selectAll`, and `join` to bind this data to SVG `circle` elements, setting `cx`, `cy`, `r`, `fill`, and a fixed opacity of 0.708. The visualization demonstrates basic data-join and SVG rendering with d3.