-For animation, moves should contains "moving" and "fading" maybe...
-(But it's really just for Magnetic chess)
-setInterval "CRON" task in sockets.js to check connected clients
-(every 1hour maybe, or more)
+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)