https://senseis.xmp.net/?AtomicBombGame

> The blast from the atomic bomb "Little Boy" above Hiroshima interrupted the game in its third day. It came at 8.15 am and at a point where the players had replayed the position - but had not yet started the game again. There were injuries to some of those there caused by flying glass, and damage to the building. Hashimoto was blown off his feet. The game wasn't resumed until after lunch. The game was then played to a conclusion, Hashimoto winning by five points with White (there was no komi). This tied the match 1-1.

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So we know what to do when a nuclear weapon goes off. You get knocked off your feat, wonder wtf is going on. Then you reset the gameboard and play your next move.