o Improved algorithm to find the start-point of an offset
  polygon. Now we are not only looking for the closest to the start-point,
  but it should be closest to the line defining the direction (which is a more
  accurate way to see this)
o Show different colors for Brim vs. not
o Make postscript-lines only 0.8 * shell-thickness to be able to
  see the spiral brim.