Why do you usually practice calligraphy with a pen, but not with a ballpoint pen? What's the difference between them?

Learning calligraphy can be divided into soft pen and hard pen. A soft pen refers to a brush and a hard pen refers to a pen. Regardless of the calligraphy of any pen, it is mainly the use of Chinese characters and brush strokes, and the use of brush strokes is mostly hidden front, center, side front, back front and hook front. Hard pen calligraphy, only pens, pencils, ballpoint pens (including water-based pens) can't. Therefore, to learn hard pen calligraphy well, it is recommended to use a pen.