With the --scale and --margin options set, time to increase the --iterations, the default value, 40/10 will typically give a rough plot with arrow collisions and unsightly gaps, increasing to 250/5 should give a much smoother look (but take several seconds to run). I don't usualy see better results above 500/5.

With reasonable plot appearance, time to adjust the visual details: the --fill opyion controls the colour used to fill the arrows, one can also control the width and colour of the pen used to outline the arrows with the --pen option.

When making these smaller adjustments, it becomes irritating to need to run the program for several seconds to see the results of a change. The --graphic-state option specifies a path to a "graphics state" file, if that file exists then the plot is loaded from it, if not then a full run of the program is made and that file is created.