What is the emphasis on the swallowtail silkworm head of Lishu? thank you

The strokes are straight, the structure is square, and several strokes are relatively fixed, which determines the unchangeable form of Chinese character writing. Transform the radicals of compound words to make them fixed and unified. For the sake of neatness and convenience of writing, official script defines the unique characters used as radicals as radicals with special forms, and at the same time fixes many seal scripts with different original radicals into the same radical, such as English, Fan, Mo, Zhen and Dian. The original seal character base is different, and the official script is unified as the "big" base. Another example is the words "Tai", "Qin", "Chun" and "Feng", which were unified into the prefix of spring only after the official reform. This makes official script easier to remember and write than seal script, and adapts to the requirements of the growing times. In the use of pens, there are both squares and circles, and the methods of hiding front and exposing front have the following characteristics: in the form of strokes, there are the characteristics of swallowtail of silkworm head, and the long horizontal paintings have silkworm head, wave potential, pitch and tail; Physically, it is a change from vertical potential to square potential and then to flat horizontal potential; Structurally, China's official position is tight, and his strokes spread to the left and right, showing a symmetrical "eight-character shape", so it is called "eight points" by Han Li. Regular script Regular script, also known as official script or original script, evolved from official script in Han Dynasty. The formation of his brushwork, the evolution from Li to modern grass. Traces of evolution can be seen from the bamboo slips of the Western Han Dynasty. Regular script was originally produced by the people, and then sorted out by the literati to standardize it. Judging from the regular script works of Zhong You, Wang Xizhi and others, this period has been quite mature and stereotyped. From the perspective of calligraphy aesthetics, regular script can be divided into three series: Jin Kai, Wei Kai and Tang Kai. The representatives of the first and third series are briefly described as follows. (a), Kincaid series to two kings as a model, the Sui Dynasty's Zhiyong is also a leader. (2) Wei Kai's series takes the inscriptions in the Northern Wei Dynasty as an example, including epitaphs, statues, inscriptions and cliff carvings. (3) Tang Kai series is based on Yan Zhenqing in the middle Tang Dynasty and four schools in the early Tang Dynasty. The main features of two or three series structures are briefly described as follows. (1) The main features of Kincaid structure are: stable and powerful; See the uniform gap; Then you can do it; Rigorous and thoughtful. (2) The main features of Kai Wei's structure are: natural curiosity; Dense and natural; It is changeable. Innocent. (3) The main features of Tang Kai structure are: stable center of gravity; Cloth and white are symmetrical; Make concessions around; Up and down. Running script (1) To simplify writing, running script simplifies some parts of regular script, or omits stippling or merges lines. For example, next to the word "Yan" of the word "Hua", the original regular script was written as seven paintings, and there were only two running scripts, saving five; The word "ran" changed from four to a horizontal line, eliminating three paintings; The swimming of the word "near" is simplified from 1.3 point bend to vertical and horizontal bend, which also saves some bending waves; The middle of the word "Buddha" used to be a deformed "bow", but now it is changed to a horizontal hook, saving two bends at once. Subtractive stippling is mostly used for radicals and radicals of characters, which is related to its frequent writing. (2) The flow direction of strokes is 1. Writing regular script with tick marks and knots is a stroke, which requires clear stippling, while writing running script can be written by stippling together, with tick marks and knots between stippling. Tick is to write short tick on points that are not tick, such as "ancient" horizontal painting and "good" sketch; It is convenient to tie the silk by connecting the unconnected points before and after, such as the middle point of "four" and the middle right point of "Xin". The tick marks between the strokes of the running script are like flowing strokes and vivid thoughts. But if there are too many hooks and lines, it will be unclean and unsightly. (2) Change the writing order of regular script and use cursive script, which is different from the original regular script, so as to facilitate writing. For example, "Autumn is full of splendor and a half", the order of regular script in each group is the first, and the order of cursive script is the second. When writing a running script, we must change the writing order according to local conditions, make the best use of the situation, and conform to the cursive script specification. Doing things at will is not only awkward, but also confusing. (3) The pen is more flexible than regular script, and the same stippling can sometimes be written like this, and sometimes it can be written like that, without restriction. For example, after the word "ge" is written horizontally, you can either flip the pen directly from the right to write a tick, or draw a small circle from the right and then write a tick; The floating goose hook with the word "leaf" can also be turned from top to bottom, or written directly from bottom to bottom; The word "wood" next to the word "wood" is usually written from the left after horizontal and vertical painting, but it makes sense to turn the pen upside down and write from the right; As for the pick next to your hand, if you write it in regular script, it is good to write a pick from the front, and it is even better to connect the vertical hook with the oblique pick with a string. (4) Running script with changeable posture is a font between regular script and cursive script. Wide range of activities and rich expressive force. There are often several ways to write a word, and its posture is changeable. For example, the four suffixes of the word "Shi" and the four prefixes of the word "Hua" are written neatly and freehand, with similarities and differences, diversity and unity, and interesting. Changing posture is the strength of running script, which is beyond the reach of regular script and cursive script. The cursive script in the pre-Qin period was quite childish and sloppy, and the degree of scribbling was equivalent to today's running script. In the Han dynasty, cursive script developed further, and in order to distinguish different cursive scripts, the names of cursive scripts appeared. In the Eastern Han Dynasty, Cao Zhang was one of the most developed calligraphy styles in the Han Dynasty, because it was easier to write. As for things like inscriptions, for the sake of prudence, we didn't find the scribbled calligraphy style of Han Dynasty like Cao Zhang. During the Southern and Northern Dynasties, it was believed that cursive script began in the Western Han Dynasty and Yuan Dynasty (48 BC-33 BC). At that time, "You's writing" Urgent Chapter "dissolved the official style, combined with calligraphy, China people's customs were simple and lazy, and they gradually went their own way", which proved that cursive script really began in Yuan Di period. The cursive scripts of Yuan Di, Cheng Di, Ai Di and Ping Di are similar, omitting a lot of strokes, especially a multi-line cylinder. Every word is bound by the words on the left and right sides, so the horizontal strokes can't be too long, and the strokes have to be recycled. When the strokes below are connected, a vertical sense of potential is produced. The number of cursive bamboo slips in the Eastern Han Dynasty increased significantly, and the fonts became more mature. The brushwork is bold and unrestrained, and the structure is open and heroic. For example, Bamboo Slips of Dihuang in the Four Years after the Founding of the People's Republic of China (23 years), especially the Weapons Book of Guangdi South (95 years), emphasizes horizontal painting, flat and long, and vertical painting is short and oblique. Thank you for answering my question in time at this late hour! thank you