Fun quiz! I had a good time muttering the German names to myself until they sounded like country names I know. ;-) You could maybe even have this be a quiz where you have to make the yellow box correspond to the clue, so that you can't just get it by typing European countries as fast as you can, haha. :-D
On a second note, maybe you should accept "vatican" for Vatican City and "uk" for United Kingdom.