What are the characteristics of the language style of Song poetry?

The language style of Song poetry is mostly plain and natural. Although some people only emphasize plain nature out of the utilitarian view of serving politics, such as Yu Wang and Ouyang Xiu in the middle and early Northern Song Dynasty, in order to emphasize "preaching and dispelling doubts", they especially advocate that poetry should be "Yi Dao and Xiao Yi"; Some people can rise to the aesthetic level and emphasize plain nature. For example, Wang Anshi said: "It seems to be the most extraordinary, easy but difficult to achieve" ("Zhang Shi"); Su Shi said: "It is dull to grow old and mature, but it is not dull but gorgeous" (Book with My Nephew); Lu You said: "The depth of hard work is flat" (Recalling Zeng Wenqing Gong). In this way, although their artistic styles are different, they all advocate natural and plain language styles, which is different from many poets in the Tang Dynasty, especially those in the middle and late Tang Dynasty who are too pursuing gorgeous or bizarre language styles.