TO DO: Add transparency and numbers - When applying transparency, treat each line and its arrowhead as one object, so the line is not visible through the arrowhead. Place the volume titles at the center of each line and align the bottom of each title with it's line (using the angle at the line's center). Avoid making any of the titles upside down. So the point of the arrow is visible, hide a small portion of the line path below the arrow.