Free the World Map by nearby World Capital in 90 Seconds
Oh no, the World Map is hardly visible, it has been covered with a grid of white boxes! Type a world capital to remove some. The boxes that will be removed are the ones where distance measured from their center is less than 25 when adding degrees of latitude and degrees of longitude.
Note that distance is measured after rounding coordinates to the nearest multiple of 5
I extracted code from this .svg file -> http://www.jetpunk.com/img2/svg/world-map-6x16.svg - quizmaster can certainly help better but I think the key is the 'styles' section at the beginning. let me know if I can be of help!
As far as I know, it's more complicated than that. You would have to change the fill-opacity to 0, then make black paths. Those black paths would be hidden behind the paths you use as answers to mask the green that doesn't appear. I'm clearly not good at explaining this, so hopefully the source code for this svg I made today will help. I had to repeat the {path d="..."} twice, one for the colors and the other so I can choose how you originally see it (when you guess correctly, it will look like the first instance. it will originally look like the second instance, in that example) Hopefully that helped, but as scambigol said, quizmaster can certainly help better :)