At each tiling level, they have a proper tiling of hexagons with 12 pentagons. The system is based on an icosahedron. But the way the hierarchical division sys

At each tiling level, they have a proper tiling of hexagons with 12 pentagons. The system is based on an icosahedron. But the way the hierarchical division system works, the tile boundaries from one scale don’t precisely match the tile boundaries from another scale.