- Zoom >= 5 shows visited regions (states/provinces/departments) colored on the map
- Server resolves places to regions via Nominatim reverse geocoding (zoom=8)
- Supports all ISO levels: lvl4 (states), lvl5 (provinces), lvl6 (departments)
- Handles city-states (Berlin, Vienna, Hamburg) via city/county fallback
- Fuzzy name matching between Nominatim and GeoJSON for cross-format compatibility
- 10m admin_1 GeoJSON loaded server-side (cached), filtered per country
- Region colors match their parent country color
- Custom DOM tooltip (ref-based, no re-renders on hover)
- Country layer dims to 35% opacity when regions visible
- place_regions DB table caches resolved regions permanently
- Rate-limited Nominatim calls (1 req/sec) with progressive resolution
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