Nice! And it's good to get a quiz that airs the perspective of the 90 or so countries that do not recognize Kosovo. There are many areas of grey in geography country quizzes.
i like the design of your other "clockwise" quizzes better - this makes it look like there's rivers separating all of them, and the black Serbian border you added is kind of awkward. that said, definitely enjoyable and i hope you make more of these :)
Btw you have written "Try whole series here here" at the top, with the second "here" being the link to the east of the series.