Round designs are used to build many intensities of shadows in a pen and ink drawing. The styles enable create lighter shadows that progress into darker ones or vice versa. This system is used to make the drawing much more organic and helps make textures like scales and foliage. https://ink-pen-drawing-technique00987.thezenweb.com/the-greatest-guide-to-how-to-draw-with-ink-pens-74760307