What are the characteristics of Yan Zhenqing's calligraphy?

Yan Zhenqing (709~785), an official of the Qing Dynasty, was born in Wanzhao, Gyeonggi (now Xi 'an, Shaanxi Province), the fifth grandson of Yan Shigu, a famous scholar in the Northern and Southern Dynasties, the greatest calligrapher in the Tang Dynasty, and a master of calligraphy art in China. He lost his father at the age of 3 and was trained by his mother, so he won the Biography of the Grass Sage Zhang Xu. He was honest and clean all his life, and served as a minister in Xuanzong, Suzong, Daizong and Dezong. He made great contributions in the struggle to pacify An Lushan, and was finally killed by the rebels. In China's book circle, Yan Zhenqing is a master of the heroic school in the past 500 years, with the most innovative spirit. After Wang Xizhi, China's calligraphy was pushed to the peak. His "Yan-style" regular script, contrary to the calligraphy style of the early Tang Dynasty, uses seal strokes. It makes thin and hard full of vigor, broad structure, majestic and strong bones, which makes people respect. This style embodies the prosperous style of the Tang Empire and opens up a new magnificent realm of China's calligraphy art. The severity and grandeur of strict laws are unprecedented; The dignified beauty and masculine beauty of Yan style set the rules for future generations. Yan Zhenqing created the sound of prosperous Tang Dynasty in calligraphy, which became one of the distinctive signs of prosperous Tang Dynasty. Representative works include Duobaota Monument, Yan Monument, Cold Food Post, Manuscript for My Nephew, Painting Praise Monument, etc.