What are the characteristics of Zhang Xu's calligraphy?

Zhang Xu is famous for cursive script, and regular script is also very good. What he wrote was not an ordinary cursive script, so he was called "Crazy Grass". What is a "weed"? That is, the style of writing is bold and unrestrained, continuous twists and turns, and the font changes countless times, but it is very organized. They often use calligraphy to express their thoughts and feelings. Han Yu, a great writer, once said in an article: Zhang Xushan's cursive script, his emotions, sadness, grief, happiness, resentment, longing, injustice and so on. All these things are felt in his heart and must be expressed in calligraphy. Zhang Xu and Huai Su ("Crazy Grass" calligraphers) pushed cursive script to a new level and made outstanding contributions to the development of calligraphy.