I reached the level, where jellyfish appears and stuck on it.
I didn't want to sacrifice tentacles and tried to kill all the enemies with "melee" attacks. It turned to be quite difficult for me, so I had to restart level again and again. After about 10th restart, game screen faded into black and stayed like this notwithstanding all my attempts to 'resolve' the situation. I could hear the sounds of the game but couldn't see it. I refreshed the page, and started the game from the very beginning, but the screen stayed black. Only restart of the browser fixed the problem, but then I began to play for the second time and happened quite the same - after about 10th restart, game screen faded into black and stayed like this.
May be it's only my problem, but also it may be a 'common' bug and admins should have a look.