A Wheel

I dreamed about the symbol for yin and yang as a rolling wheel and then it made even more sense to me.

Yin and yang transform each other: like an undertow in the ocean, every advance is complemented by a retreat, and every rise transforms into a fall. Thus, a seed will sprout from the earth and grow upwards towards the sky—an intrinsically yang movement. Then, when it reaches its full potential height, it will fall. Also, the growth of the top seeks light, while roots grow in darkness.
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