Some feedback

[PKJonas]

Here are some things that could be improved in your solution:

• Instead of (Double, Double) you could have a Coordinate case class;
• Instead of Seq[Seq[(Double, Double)]] - MultiPolygon(List(Polygon(List(Coordinate)));
• Lack of unit tests;
• Some unsafe places in the code (polygon.head for example can throw an exception; so could pair(0) -> pair(1)), so the solution wasn't tested with empty polygons or invalid args.
• Code could be organized better - json, arg parsing, logic could be put into separate files.
• isLocationInRegion looks rather scary and could use some comments, or nested methods that have descriptive names;
• The repo contains a jar instead but does not explain how to build it;

[PKJonas]

By the way, if this was your first crack at writing Scala - good job!

[SCRIPtRaven]

I was able to implement unit tests, fixed the unsafe parts of the code, organized it into separate files based on different concerns, refactored isLocationInRegion to have nested methods with descriptive names and even added small comments what each nested method performs and why. Also updated README with instructions on how to build the jar file. However I was not able yet to implement the first two suggestions because as it is now, the JSON files are parsed directly into case classes, and to modify them as suggested requires using case classes that consist of other case classes. I have attempted to do it, but unfortunately so far I have failed to parse the JSON files correctly into said structure.