Everyone loves the El Farol Bar in Santa Fe, New Mexico (especially W. Brian Arthur, who wrote this puzzle in 1994).
That is, everyone loves the El Farol as long as it's not too crowded
If it's less than 60% full, it's more fun to be at the bar; if it's more than 60% full, it's more fun to stay home. This puzzle has one more catch: everyone has to decide whether or not to
go at exactly the same time, without communication.
So what should you do—stay home or go to the bar?
You can probably see the Catch 22 here.