Let’s play. Those words, delivered to a small group of like-minded people you trust, are the surest way I know of finding a creative solution to some problem. But the mood that makes play possible is fragile: one difficult person, one sharp comment, and it vanishes like a soap bubble and you will struggle to recover it. So when we set out to invite a room of 100 people to play, it was with some trepidation. These were highly successful,