Coverings

Toggle any selection of countries (each from polygonToCells, merged into one covering) and place two spherical caps around European capitals with sphericalCap. Each is a covering; combine any two with union, intersect or difference.

The set operations work directly on the compacted cells, which cover contiguous runs of the A5 curve, so nothing is uncompacted. The result is compacted too: darker cells are coarser.