There is a way to pause the game. Right-click on the game screen to bring up the popup menu (Zoom In, Zoom Out, Show All, etc etc...). If it doesn't pause, click on the game screen to get rid of the popup, then retry right-click. Repeat until the game pauses. Sometimes it works, sometimes it doesn't, just keep trying until it pauses.
It works on my browser (Google Chrome). I don't know if it works on IE or Firefox.
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