First choose any Europe 10K+ pop city by entering it and choosing it in the drop-down box. Then, name any Europe 10K+ city in each 100 km circle/ring as the rings expand outward from your city of choice, trying to name SECOND LARGEST city in each circle. The first circle will include your city of choice as a possible answer.
PLEASE NOTE - You must type a '.' (period) after each city to submit it to prevent answering another city with a name you would be have to type to get your answer. If multiple cities have the name you submitted, only the largest one will be counted.
You accumulate points based on the population of the city you named in relation to the second largest city in the circle. A smaller city’s point total will be the ratio of its population to the largest, so if you name a city of 75K people and the largest city has 100K, you get 75 points. Naming the largest city will get you points based on the ratio of the 2nd largest city's population to the largest city's.
When you run out of time or end the quiz, you will see the current ring’s 2nd largest city at right (under ‘Answer Stats’ by your coordinates).
For example, if you choose ‘Paris’ – you will be shown a circle of radius 100 km centered at Paris. Naming any city in this circle (including Paris) will cause another ‘ring’ of radius 100 km to appear outside that circle, however - you will want to try naming the SECOND LARGEST city you can to get more points. After completing that circle, you now need to name any 10K+ Europe city in the new ring (but not within any previous circles/rings), again trying to name the 2nd largest city. If there are not two cities within the next ring of that distance, the ring will keep expanding by that distance until two cities fall within it.
Quiz Takers 
I think it’s a bit silly to have 10 km be the cutoff distance when many cities are bigger than this. Especially considering the fact that multiple cities are combinations of two that each have their own city center. If you click in the middle of Sarpsborg, it will make you lose on Fredrikstad/Sarpsborg because it’s more than 10 km from the middle of Fredrikstad. Ideally clicking anywhere within the urban area should give you 0 km.
I changed the multiple cities ones to show only the first city (where the marker is).
Hey, really happy to see Norway be the next country out for this quiz being Norwegian myself! Just a little feedback: It feels strange seeing Stavanger/Sandnes, Porsgrunn/Skien and Fredrikstad/Sarpsborg being merged together, seeing as they are all separate cities and municipalities. Similarly, Fetsund-Ostersund should probably just be Fetsund, and same for Orkanger, Algard and Kleppe, since they almost always mentioned by just that name.
I know that the Norwegian census sometimes does funny things in regards to what they count as a separate urban area, so I presume it’s something there. I’ll comment if I find some more 🙂
Keep up the good work!
Yeah I go by how my source citypopulation.de lists them, which is how the Norwegian Census counts cities I guess.