回 | huí

In Mandarin Chinese, 回 (Pinyin: huí 🔊) means “to return”, “to turn around”, “to reply”, or “to decline”.

There is a variety of historical forms of this character, including concentric circles and spiral shapes. For handwriting purposes, I think it is still easier to draw a spiral than a pair of concentric squares.

More photos of spirals and sea glass @ Shutterstock.