Please, if you show me a list of things, let me use my arrowkeys. Also, can you finish more gracefully than giving my undefined?
Also, I opted for Tab completion instead of arrow keys; it's much faster and far less finicky to implement robustly.
Edit: Actually, it just turns out (after reading the source) that in some cases it just won't accept the answer if it's wrong. I did the honourable thing and selected "Forfeit", allowing me to continue :)
It's a small thing (and I did like it once I realised how it worked) but when doing things in an unusual way a little bit more guidance is required at first.
Enjoyed the quiz!