-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)
+Finish rules translation in Spanish
+Design: final touch (gain extra space on top, using space on the right)
+Crazyhouse: center reserves, grey if zero available, numbers superimposed