This example shows a single blue circle centered within a 200-by-200 SVG canvas. The circle has a black stroke and a fill color of #69a3b2, demonstrating basic shape rendering with D3 v5. The code creates an SVG container using `d3.select("#circle").append("svg")`, then appends a circle element with attributes for position, radius, stroke, and fill. Though the title references a rectangle, the visualization actually renders a circle using standard D3 selection and attribute methods.