This has been an explosive summer — markets in turmoil, cities in flames, politics in meltdown. So it’s a relief to enjoy and learn from an explosion of a different sort — the explosion of creativity taking place this August in Edinburgh, Scotland, at the renowned Edinburgh Fringe Festival. The festival, a one-time icon of artistic rebellion, is now the largest arts gathering in the world. It is also an entertaining case study in the power of grassroots innovation and open-source creativity, a positive symbol of how unchecked human energy, shaped by a few simple rules, can unleash truly amazing results.