Doesn’t Ark kinda do this, except with elevation, it becomes more difficult the more inland you travel.

BTW the newer RotMG maps are based on this http://www-cs-students.stanford.edu/~amitp/game-programming/...

One of the map design goals in RotMG was that players could start playing solo on the coasts, and then as they moved up towards the mountains, the area would shrink so they would be more likely to meet each other. However, when we added teleportation the "forcing function" wasn't needed anymore. Players naturally wanted to play with each other. Also, a lot more players were high level so we needed more mountain land and less coastal land. For https://gasgame.net/ we're using a different design, where south is easier and north is harder. Relative to RotMG's map it shrinks the beginner areas and expands the veteran areas.