上下颠倒的地图则展示了一个不同的世界。
它们是透镜，因为它们是凸面容器，当它们盛满水后，它们可作为透镜使用，你可以看到它们里面上下颠倒的地平线。
They're lenses because they're convex vessels, and when they're full of water, they act as a lens and you see the horizon in them, upside down and backwards.
一个多么上下颠倒的星球阿？ ！
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