Quite often the mouse button is blocked/disabled in the upmost area of the game window. All buttons (raiding, farming, etc) are unclickable. This applies also to the close icon of popup windows. I have to reload the game.
Since it's the only game on Kong where I observe such an effect, I assume the reason lies rather in this game than in my browser.
There are some floating point display problems on higher levels ("249,99999999999997")
Also around level 18 the balance is lost. The income increases faster than the costs, I couldn't upgrade these guys as fast as the money was produced.
But it was fun anyway :)
It's a bug, will fix.