Zhang Huaiguan in the Tang Dynasty said in the "Introduction": "It's hard to inquire about the eight styles, and the brushwork is dangerous. The seal character is particularly refined, flying white, as steep as the ancients, like a dragon and snake fighting, with light clouds and light wind, and the wind is thundering and the exercise is like a god. " The decay of the true line comes from the big order, so don't become one. As dense as an armory spear and halberd, Shen Feng is stricter than wise water and less polished than Shinan. His cursive script is circulated, which can be regarded as two kings, and can be used as a dynamic color, but it scares him to jump, does not avoid danger, and hurts elegance. "