什么环是方形的？

What ring is square?

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从远处看像一座巨大的拱门，它是一个连续的环，像一种方形面包圈。

Looking from a distance like a gigantic arch, it is a continuous loop, a kind of square doughnut.

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但它的挑颜色却相当简单，只需画一个一个长方形的撑住色相环；这样，矩形的四个角就会各压住一个色相。

Picking the colors for these is fairly straightforward, one simply draws a rectangle over the color wheel; each of the corners anchored to a particular hue.

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