How to understand the horizontal trend of characters in calligraphy

The gesture of a word is expressed by the comprehensive action of the pen gesture, which often shows a distinct movement trend. For example, we often say that a word shows a vertical trend and a word shows a horizontal trend, which actually means that the word shows a vertical or horizontal movement trend. Various fonts of Chinese characters often have specific styles, such as the vertical trend of Xiao Zhuan and the horizontal trend of Li Shu. The static potential of objects, the dynamic potential of grass, and so on. The works of various calligraphers also show different trends, such as the steep trend of Mi Fei, the trend of Li Yong and Su Shi, and the radiation trend of Huang Tingjian ... Wang Xizhi's book has no definite trend in structure. Taking Preface to Lanting as an example, its structure is sometimes scattered and sometimes tight, and there is no trace of carving.