which has been removed from the mainline in 1.15.3. Unofficial campaigns are translated into many languages the same way as the official ones. Some of them are very long and well balanced, like "Invasion from Unknown", while others serve to show units not available in the mainline, or as examples for future campaign makers, like "A simple campaign" or "The Final Exam". The longest unofficial campaigns have more translatable strings than the longest official campaigns. Modding Add-ons It is possible to create and distribute additional content (user made content, or UMC), such as campaigns, maps and multiplayer "eras" using an "add-on" system. These add-ons can be downloaded, updated and removed using an in-game add-on server; alternatively, they can be installed and updated by manually downloading the add-on's files and placing them in the appropriate directory, or they can be removed by deleting these files. Editor The Battle for Wesnoth has a built-in map editor, which supports features such as multiple open maps and random map generation. The editor supports all in-game terrains, as well as custom terrains created for campaigns. The time of day can be selected from one of the built-in presets or custom lighting can be created. WML Using any standard text editor, new content can be created using what is known as Wesnoth Markup Language (WML). As its name suggests, WML is similar to XML and other markup languages in syntax with tags defining events and sides in a scenario. WML has evolved from what was a simple markup/configuration language into a specialized programming language designed for easily modifying the game. Examples for the latest stable version are offered on the site's wiki. Lua From the 1.7 development version upwards, code in Lua can be embedded in WML events which gets executed when those events fire. From 1.7.14 on, Lua can also be used to create alternate (or supplemental) AI implementations. Development Version Besides the official wesnoth game version, there is always an alternative development version, that introduces more new features and improvements for players and content creators. This development version is rolling subject to further tweaking and polishing, depending on the wesnoth community feedback. There is planned to deliver a high-quality and stable 1.12 release in the future, which could feature a seventh default faction, called Khalifate. It should offer fresh and interesting multiplayer options. Khalifate units use no magic, but instead rely on careful use