What achievements has Huai Su made in calligraphy?

Huai Su (725-785, 1737-799) was a calligrapher in the Tang Dynasty. He is diligent in learning books and is famous for being good at Weeds. Good at drinking and writing, like a whirlwind of showers, flies around, although there are changes, but the statutes are available. Old age is often dull. Predecessors commented that Mad Grass inherited and developed from Zhang Xu, calling it "following the madness" and "getting drunk", which had a great influence on later generations. The surviving books include autobiographical notes, bitter bamboo shoots, and essays in books.