Just as physical activity is essential to maintaining a healthy body, challenging one's brain, keeping it active, engaged, flexible and playful, is not only fun.

正如身体活动对保持健康体魄很重要一样，挑战人们的大脑，使它保持活跃、参与、灵活和有趣，不仅是一种乐趣。

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But, of course, it wasn't designed to just be fun -- it's about comfort and not keeping your arm or hand still for long periods of time.

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