Post #1810164

@fraggle@social.coop no! Another group of friends did once ponder time-travelling chess, but without a multiverse component. The motivating example is that we're playing a perfectly normal game, and then on my turn I reach into the spare pieces box and put down an extra queen on the board. But then later in the game I _must_ send my existing queen back in time in such a way that it would arrive where and when that extra queen materialised, or else I forfeit the game by causality violation. But we couldn't think of any way to fill in the details that didn't make it essentially suicide to use this ability, because it would be so absurdly easy for the other player to _force_ you to turn out to have violated causality!