The word "sheng" in the sentence "The incense burner in Rizhao gives birth to purple smoke" in Du Mu's Autumn Night is a variant. In general, the common spelling of "sheng" is "sheng", but in ancient calligraphy, there is a way to extend the right side of the word "sheng" downward to form a small hook, which is the shape of "sheng". This writing style is called "cursive script" in calligraphy, and it is a fluent writing style. In ancient poetry, this writing style was sometimes used to increase the artistic appeal of poetry.