Hopefully not: Let's play nuclear war.

The "Nuclear War Simulator" describes itself as a detailed, realistic simulation and visualization of large-scale nuclear conflicts focusing on humanitarian consequences.

The simulator allows you to design warheads, missiles, and carriers, place them on the map, and execute attack plans to create a credible narrative of how nuclear conflicts unfold and their consequences. With a high-resolution map of population density and realistic weapon effects such as explosion, heat, and radiation, you can estimate how many people will die in a conflict. In short, "Pretty serious stuff!"

Definitely not a game for casual play or for fun, because no matter who starts in this game, everyone loses in the end. More information about the game can be found on their website.

Nuclear War Simulator online