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 
Kick Russia out and we are golden…Apart from that great quiz
Great quiz but way too little time. 6 seconds per city is just not enough to zoom out, zoom in and search.
I’ll bump it up a little bit.
I don’t think cities like Chelyabinsk belong to Europe as they are east the Ural mountains
It’s a judgment call – they are very close, and other popular quiz sites use them as part of Europe.
it seems to give 99 instead of 100 even when distance is 0 km, is that on purpose?
also when the time went to 0 it shows 0:-1 says Finish all cities to submit score and the quiz doesn’t end