-Set problems style (maybe will fix strange flashing bug?)
-global lang cookie, + display (remember in each variant what is shown...)
-translations (how ? switch on index page only, then find ideas...)
-Improve style for various screen sizes
+Checkered chess: need another FEN element, last non-capturing checkered move (if applicable)
+ + need to stack these indicators for alpha beta search
+MarseilleChess: revise bot and test
+Translations (including About page), refresh rules