Neat idea, but I found easy mode trivial and medium mode completely impossible (had never heard of most). I think it needs better hints, or warmer-colder info or something. I think it would be more fun if it was a way to learn as much as a test of what you already know.
Good job! Is the layer with the cities names supposed to appear too? I would have a lot more fun having only countries names appear on the globe and trying to guess the location of the city within.
Very interesting, it would be great if where we could include/exclude continents in custom mode.
Cool game! For US cities add the State abbreviation as well in the question because city names are not unique across USA. For example there is a city called Lexington in Kentucky, Massachusetts, Alabama, Georgia, Illinois, Indiana, Kansas, Maine, Michigan, Minnesota, Mississippi, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Virginia, and Washington.