I would prefer a mode without a timer. Especially on the explanation page after a question.

There are a couple questions I encountered with wrong answers. One question asked me to solve x/4=3 and then insisted that the answer was 24, which is wrong. Another asked: “if you have 3 apples and you take 2 away, how many do you have?” It insisted that the answer was 2, but since the question clearly states that I have three apples, I insist that the answer is 3.

Otherwise, great website! I like how well it works on mobile, good job.