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 
need to allow full screen mode and also make the correct marker a different color (currently both are green if you guess close)
Kinda hard to click on phones and tablets but it’s like this everywhere so it’s not that bad
How does the quizz start ?
was a bug – fixed.
why for 0 km you still get 99 and not 100
You can always use the zoom function though admittedly it will make you lose some time zooming in/out and moving the map around. Previous locator quizzes were not timed so it adds an extra challenge.
A little hard to click precisely when places are so close (especially around Paris), but nice quiz.