2 / 3 / 4 hour zones follow real roads (Matrix sample points + Turf isobands). Day-trip range only. The nearest 24 resorts use Mapbox drive times; farther ones use air-distance estimates.
A few Matrix batches time a grid around you, then Turf draws isobands. If the grid is too sparse, a drive-time heatmap is shown instead. Click a name to fly there.