不过，看看你能用指尖平衡铅笔多长时间也很有意思。
However, it's still fun to see how long you can keep a pencil balanced on a finger tip.
面向墙站立，指尖扶墙然后用一条腿保持平衡。
Stand facing a wall and place your fingertips on the wall and balance on one leg.
这是一个不稳定系统，就像尝试平衡立在指尖上的铅笔一样。
This is an unstable system, like trying to balance a pencil on your fingertip.
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