After checking my answer, at the moment if I get it wrong, in dark mode, the correct answer is not readable. I think it's purple text on a black background. I tried it in light mode, and it tells me I got it wrong, but it doesn't tell me what the right answer is so I have to start the quiz all over again to find out. Obviously I quit using the quiz. Like this, it's only really useful if I've got a 90% success rate.