The 12-country selection's terrain.pmtiles was headed well past the 181GB an earlier 5-country build already produced at z15. Raster DEM tiles don't compress away like vector ones (every tile is a real image, even over empty terrain), so each extra zoom level roughly quadruples storage. z13 is each Mapterhorn regional chunk's own native minzoom — one raster level per chunk instead of a 15-13=2-level pyramid on top — still enough for the hillshade toggle and the planned slope readout. Online hillshade keeps its own z15 cap; this only affects the offline copy.