Another Listener with no PDMs, like the one by Gos - just tinker away hoping it will all be worth it in the end.
I can't understand what is meant by 'in the 12 cells', as there are 18 in each circle. Having solved only 13 and 22, with absolute certainty, I find they don't match up to the letters in the convex cells, so what do I have to do? Select 12 cells at random, combining convex and concave?