This is a custom map mod, which is still in development, the map plan is to have at least 6 custom maps, with at least 2 bonus maps.
This is the second level of this mod called "Korean Island." It's two Islands full of enemies for you to kill. For some reason there's this bugged rock that you can't see in the editor but you can see it in game so you can't delete it. Good thing there's another way around.