Upon clicking START you will be shown 5 circles, one at a time, with increasing radii: 50, 100, 250, 500 and 1000 km. The object is to move the circle to the location such that it covers the most amount of people, based on Europe population density data. You are scored based on how many people you cover compared to the maximum possible (score is based on the ratio of people in your circle compared to max possible - score is not an exact ratio but falls faster than that).
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 
I encountered a weird error – I typed in Spain and it brought up a list of what I presume to be the largest cities per letter per country, sorted by population. I typed in a bunch of cities it would “take” my answers but nothing was revealed and my score was [answers]/0. I kind of have an unbeatable score in Spain now though, lol.
Forgot to add – issue was gone on refresh. Probably just an issue with not loading the country – the country listed was on the side, but it was clearly pulling from all European countries.
hmm must be a one-off bug – i’ll remove that score.
For the Netherlands, you included a category which starts with an apostrophe (‘). The answer for that character is given as ‘s-Gravenzande, while ‘s-Hertogenbosch is the given answer for ‘S’. ‘s-Hertogenbosch is correctly written with an apostrophe though, and should be the answer for that category instead of ‘s-Gravenzande. Or you could remove the ‘-category entirely.
yeah I’ve fixed this – the apostrophe shouldn’t have been included as a letter.