The terrain map editor allows users to select individual tiles (you may select many at once) and assign a new terrain type to each. There are currently a limited selection tiles (this is temporary - we have dozens of compatible tiles which will eventually enable adding of multiple terrain types, rivers, paths, cities, etc). Simply select the tiles you wish to change, choose a new terrain type, and submit. On submission the changes are stored to the database and the editing page will refresh showing the results of your changes. All changes are fully stored on submission - you may return to edit at any time after. Maps are not limited in size - so large maps will take time to edit!