Had a Jane Street interview in 2014 Round 7. Interviewer says 'meet me at Washington Square Park, southwest corner, 2 PM.' I show up. He's playing chess with a guy who's clearly hustling tourists. Interviewer's losing badly. Without looking up he says, 'Take my position.' I sit down. The chess hustler looks at me and grins. 'Your boy owes me $40. You covering his position?' I look at the interviewer. He nods. 'Assume the debt,' he says. 'Now optimize.' I study the board. I'm down a queen and two rooks. Completely hopeless. 'This position is unwinnable,' I say. 'Correct. Now make it profitable.' 'What?' The chess hustler is getting impatient. 'You playing or what, kid?' The interviewer slides me a $20. 'Market make this game.' I'm confused. 'How do I market make chess?' 'Bid-ask on the number of moves until checkmate. Hustler takes the under, you take the over. Spread is your edge.' I look at the position again. Maybe 8 moves max until I'm mated. 'I bid 12 moves, offer 15,' I announce. The hustler laughs. 'I'll take the under on 12 all day.' 'Done,' says the interviewer. 'You're now short volatility on a deterministic outcome.' Three moves later I'm checkmated. I owe the hustler $40 plus my $20 bet. 'How confident were you in that 12-move bid?' the interviewer asks. '0.95,' I say, because that's what you always say. '0.95 huh?' He chuckles. 'You just sold insurance on the Titanic.' He stands up. 'The real trade was shorting your confidence and going long on the hustler's experience. You missed the obvious hedge: offering chess lessons to tourists at $25/hour while the game played out.' 'But I don't know how to play chess well enough to teach.' 'Exactly. That's called selling vol you don't have. Very Jane Street.' Offer rescinded. Reason: 'Failed to recognize that the park itself was the market and the pigeons were the only rational actors.'"