Thanks for checking it out. a) seems like a bug, but I can't recreate. After I click "next" for the next problem, the answer field is empty. Let me test some more b) yes, this is indeed a weird UX and my daughter said it is "annoying". But it exists so that the kid gets a pause to know whether the answer was right or wrong. I should maybe show it for 3 seconds and proceed to next automatically.

Will upload new version of the site tomorrow now that I have a full two users for the app :)