What does the West Building mean in classical literature?

The west building is usually associated with the moon. I feel sad when I see the waning moon. The west building should be a small building built in the west of the main building, with the stairs facing east. In ancient literature, the West Building is often associated with the image of the moon, because it is convenient to see the moon in the west, especially the sinking moon, which is the moon in the middle of the night. Give a few famous sentences about the West Building, such as Li Yu's "Alone on the West Building, the moon is like a hook"; Li Qingzhao's "When the geese return, the West Building will be full in the next month"; "Because of your promise, I have been watching the full moon come and go in my western tower." To My Friends and Harmony by Tang Dynasty poet Wei. ; Xin Qiji, a poet in the Song Dynasty, wrote in "The Red River": "Go to the West Building quickly, lest the sky release Yun Zheyue. But when you scream, the jade woven flute will crack with a big blow. Who will be the most regrettable person in curling in the season? Ask Chang 'e, loneliness should be happiness. " ; Yan, a poet in the Song Dynasty, wrote in Death: "The West Building will not wake up until it is drunk. Spring dreams and autumn clouds are easy to gather and disperse. I still sleep less at the half-moon window, and the screen is idle. "Li Yu boarded the west wing faintly." Without words, he went to the west wing alone, and the moon was like a hook, and the solitary Wutong courtyard was locked in the clear autumn. "alas! Looking from a distance, I saw the crescent moon as a hook. Looking carefully, I saw that the children's voice was locked, and it was really nostalgic between pitching. There is also Li Qingzhao's "When the geese return, the West Building will be full in the next month". Yiren in the west building is independent, the full moon is not full, the geese are not home, and the delicate woman wants to wear it, full of sorrow! It's really depressing and tearful! In the Book of Changes, Xi is a girl, so the ancients often lived in the west wing according to the principle of geomantic omen, that is, the unity of heaven and man. In China literature, the moon is the image of acacia, so the west wing is mostly related to boudoir thinking, which is convenient for watching the moon in the west wing in the middle of the night. It can be seen that people who watch the moon miss it so much that they can't sleep. The western five elements belong to gold, the season belongs to autumn, and the gold owner. So "West Building" is used to write about missing people on a moonlit night or being sad in the middle of the night. Gradually, the "West Building" has evolved into a synonym for lovesickness and sadness in ancient poetry, just like the "willow branch" in ancient poetry represents the feeling of parting.