There has been a problem which I have experienced and reports of similar issues from users regarding occasional freezing of the game. I have made some changes that have hopefully fixed the problem and I have not been able to reproduce the bug since. Any errors can be reported through the Feedback page on the site.
If the problem persists it is possible to continue the game simply by refreshing the browser - reloading the site. The game will be restored to the last save instance.
