Sustainable Playing

Each iteration has a fixed size of 180 seconds. Before implementing each story, the players devise their strategy. The hourglass is started when the implementation starts. When the team thinks it has completed the story, the hourglass is stopped. The hourglass only measures real implementation time.

The implementation time is very stressful, because the players try to complete a task in only a few tens of seconds. The players can relax a bit between implementations and discuss their design and strategy. This simulates the XP practice of sustainable pace or "no overtime": Developers work with full concentration on some task, go home, relax, and come back the next day, ready to perform another task.

Despite the concentration and stress of the story implementations, the players don't feel tired after three iterations. That's because they enjoy what they're doing, and they get time to relax between tasks.