At the command line, enter ucs, and choose to rotate the x axis by 180 degrees. This is rewritten text. You found that the zero-degree prefix was washed down. At this time, you will find that the prefix is washed up again, because the plan command also rotates the observation angle of the screen by 180 degrees.
The three axes of ucs are simple. Entering ucs, cad CAD will let you enter the first point, the second point and the third point, which correspond to the origin, x and y respectively.
If xy is clockwise, z is (0 0-1), otherwise it is (0 0 1).
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It was supposed to be marked with coordinates I added you. I will give you a tool developed by myself, which can achieve the effect you want.