[lambda_cube]

I know, I had trouble with that as well, but then I read the explanations you get if you click the question mark in the upper right corner. I will try my own explanation here.

Type your answer in the box, if you type 2 or more characters, there will be an auto complete list of matches.

If nothing happens when you choose an answer, then it's wrong.

When you choose the right answer, it will immediately switch to the next question.

If you don't know the answer you can click Forfeit or press Esc. To get rid of the correct answer that pops up when you do so and go to the next question, you have to press Esc (I didn't find a way to go to the next answer just by clicking with the mouse).

[14113]

The question mark doesn't even work for me (chrome linux), and no code is shown.

[EDIT] My mistake, all you have to do is turn off https everywhere, or reload using http. Frustrating, but not 100% broken...