The cartridge can be played anywhere over the World, however the cache place is close to the city center of Sofia, Bulgaria.
You will get a series of 15 questions on well-known numeric sequences. Each correct answer gives you 10 points. The more points you gather, the more accurate coordinates you will get. If you answer correctly all questions, you will also get a bonus hint.
The coordinates for the physical cache box where you can sign the logbook will be displayed at the end of the questionnaire (perhaps).
Good luck!
In case the cache is missing I will appreciate if you place a temporary container until I do maintenance. Happy geocaching!