Simulating the Effects of a Nuclear Detonation

Have you ever wondered how [the nightmare of] a nuclear detonation would affect major cities? There's Nukemap, by Nuclear Secrecy (lol?). It's a Google Maps based app that allows you to select various existing nuclear weapons, or create your own, and test them on major cities around the world. You can even test a missile launch by North Korea on the US.

It's fun to play with, but horrifying to think about.