This example demonstrates an interactive map of Spain’s autonomous regions using the d3-composite-projections library to combine separate projections into a single visualization. It loads preprojected TopoJSON data from the es-atlas package and renders boundaries with `d3.geoPath`, while a dashed brown overlay marks the composite projection’s internal borders. As the user moves the mouse, the code uses `projection.invert` to display geographic coordinates and appends fading circles at each cursor position, using SVG transitions to shrink them. Points outside the valid projection area trigger an error message instead of drawing.