Under construction, a way to create radial gradients with a non-linear distribution. You can define 1 or 2 gradients plus a background tatami. Since doing concentric circles with turtle geometry is beyound my skills, I imported the circle centre function. The gradients are linear, i.e. a steady increase of the distances between the circles. For real world use, export to SVG, import to Inkscape, then adjust a few circles, using CTRL_( and CTRL_). It's in french because of the target population....