-End of game a bit too verbose: should just say "Black win" ... + show PGN
-Styles must be improved (full width for smartphones, selectable text for PGN...)
+Finish showProblem() in components/problemSummary.js (send event with infos, and pass message to game component)
+Add new mode in game component: "problem", in which we show description + hidden solution (reveal on click)