It complements https://nuclearsecrecy.com/nukemap/ nicely. As someone not living in the US, I'd find it interesting to at least have some other non-US cities available in the free plan though.

Something that I always wondered about this tool, and why I bucketed it in my mind as a "cool but ultimately boring toy" - why are all effects perfectly spherical? Surely the actual effect, especially for lower-yield devices, would be meaningfully affected by local topography and even buildings?