Japanese can be read left-to-right, top-to-bottom (like English), or top-to-bottom, right-to-left (traditional).
Place some Japanese text in a rectangular grid such that both reading directions make sense but they have radically different meanings. One kana per grid box, some boxes may be empty.
One could also do it with English. Boxes might have a single letter, a portion of a word, an entire word, or blank space. The alternate reading direction would probably be top-to-bottom, left-to-right.
In the Sator square, 4 different directions of reading surprisingly all yield the same message.
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