The stroke order of Dan Zi in calligraphy

What the school teaches is to go up first, then down, first left and then right, then to the middle and then to both sides.

But in fact, if you are writing calligraphy, there should be no formula. Especially cursive script (but cursive script has a standard knot), so does seal script. Therefore, writing calligraphy can be done spontaneously, and you don't have to stick to the order of strokes, but you can't change the words at will.