I've indeed had messages about the game being a bit laggy for some. Are you on a laptop without a graphics card perhaps? It seems to run sub-optimal without a dedicated graphics card.
2 things I can try to recommend:
-If you played on the browser, try it in Chrome, and check if you have Hardware acceleration enabled in chrome's settings somewhere.
-If that doesn't work: try downloading the game to your PC and run it locally, if that one also lags it could be a system requirement issue.