anchor.diff:                     :x (random width)
                      :color-pair (list :black (nth (random 7) colors))))))))
   
  -;; https://blog.chaitanyagupta.com/2013/10/print-bit-representation-of-signed.html
  -;; https://jonasjacek.github.io/colors/
  -;; http://stackoverflow.com/questions/25091638/other-colors-in-ncurses
  -;; http://stackoverflow.com/questions/15105055/c-brightyellow-and-brightgreen-colors-ncurses
  -;; https://en.wikipedia.org/wiki/256_colors
  -;; http://www.robmeerman.co.uk/unix/256colours
  -;; https://askubuntu.com/questions/821157/print-a-256-color-test-pattern-in-the-terminal
  -;; https://gist.github.com/mgedmin/2762225
  -;; https://serverfault.com/questions/90296/what-are-the-color-names-in-term-xterm256-for-colors-16
  -;; https://gist.github.com/MicahElliott/719710
  +;; it is just a coincidence that "echo" works here.
  +;; echo is a chtype-function, and chtype allows only 1 byte for color pairs, which means 256 color pairs.
  +;; it works only because the foreground color is always black in the example.
  +;; echo-wide-char has to be used.
   (defun t20a ()
     "Display the 256 supported colors. This only works with TERM=xterm-256color in xterm and gnome-terminal."
     (with-screen (scr :input-echoing nil :input-blocking t :enable-colors t :cursor-visibility nil)
  
positive.code:     (loop for i from 0 to 7 do
           (loop for j from 0 to 1 do
                (loop for k from 0 to 2 do
                     (echo scr #\space :y j :x (+ (* i 3) k) :color-pair (list :black (+ i (* j 8)))) )))
  
      ;; 16-231: 6x6x6 color cube
      (loop for n from 0 to 1 do
           (loop
  
negative.code:               (loop for i from a1 to a2 do
                     (loop for j from 0 to 5 do
                          (loop for k from 0 to 2 do
                               (echo-wide-char scr #\space
                                               :y (+ 3 j (* n 7))
                                               :x (+ (* (- i a1) 3) k a3)
                                               :color-pair (list :black
                                                                 (list :number (+ (* n 108) i (* j 6)))) ))))))
      ;; 232-255: 24 shades of gray, without black and white
      (loop for i from 232 to 255 do
           (loop for k from 0 to 2 do
                (echo-wide-char scr #\space
                                :y 17
                                :x (+ (* (- i 232) 3) k)
                                :color-pair (list :black
                                                  (list :number i)))))
  #|
      (loop for i from 16 to 21 do
           (loop for j from 0 to 5 do
  