same for me, but I tried on another screen and it works. not sure what the problem is but if anyone has the same issue, try it on a different screen. It's worth playing it.
Any chance you are playing on a monitor with higher resolution then 1920x1080? We are unsure why but, if you drag your browser window to a monitor that is 1920x1080 the animation will continue and move off the screen allowing you press the play button, sorry for inconvenience :(
