The object of this quiz is to adjust each circle's radius so it contains the target population shown at the right but ONLY within Europe. When you click Start you will be shown a marker on a random populated Europe grid square (there are over 90K 10x10 km grid squares used for the data, courtesy of https://human-settlement.emergency.copernicus.eu/index.php). Also you will see an adjustable circle of radius 100 km to start. Adjust the circle's radius by dragging it until it contains the target number of people shown - this target will be between 5 and 100 million people. Then click submit. You are scored on how close your circle's population is to the target.
PLEASE NOTE: ALL of Turkey is included in counting population (not just European portion), and the portion of Russia west of 61.5 degrees E (just east of Chelyabinsk). Nothing outside Europe (such as Africa or middle east other than Turkey) is included toward the population count within a circle.
Quiz Takers 
Can you make some of these for Africa, South America, and the Middle East? Also, how about coverage for cities starting with the same letter as their country? You could even break that into separate versions for each letter.
I would love to have this quiz for other continents as well! As far as I can see, there is only a World version and a Europe version. That should be relatively easy to make, right?
I have Ioannina, Ierapetra, and Ialysos in Greece, but for the life of me I either cannot find the fourth city, or cannot come up with the proper spelling. Is there a listed source somewhere?
Did you ever figure it out?
Imittos