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 
Helgoland, Koserow and Selfkant aren‘t cities, why are they included on this quiz? Or does it count all municipalities, regardless of their official classification?
they actually are counted as settlements/communes by the German census
It´s usually spelled Heligoland, not Helgoland tho
i’ll change to accept both.
That’s the English spelling, in German it’s Helgoland
On int difficulty, in the square in the northeast around szczecin/stettin, the largest german city is definitely schwedt/oder (33.524 inh.), but it doesn’t accept this nor any other significant town in the region as solution
Found the problem: some towns with “/” in their name are only accepted without it, so “schwedtoder” instead of “schwedt/oder”