Drawing validity

When you begin drawing, you may see that part of the world is grey, instead of the usual color. The parts of the world that are colored this way are not valid locations for your selection. If a part of your selection overlaps with these areas, that part of your selection will be red instead of green. This means that part of your selection is invalid (for example, because you try to place a building, but a building already exists in that location). When applying your selection, the red parts are ignored. Only the green part is applied.