Level design, environment design, or game mapping is a discipline of game development involving creation of video game levels—locales, stages, or missions. This is commonly done using a level editor, a game development software designed for building levels; however, some games feature built-in level editing tools. Level design is both an artistic and technical process. Level design, environment design, or game mapping is a discipline of game development involving creation of video game levels—locales, stages, or missions. This is commonly done using a level editor, a game development software designed for building levels; however, some games feature built-in level editing tools. Level design is both an artistic and technical process. In early days of video games, a single programmer would create the maps and layouts for a game, and a discipline or profession dedicated solely to level design did not exist. Early games often featured a level system of ascending difficulty as opposed to progression of story-line. The first game genre that required significant amounts of time to design areas were text-based games, such as MUDs. Often, promoted users were assigned to create new paths, new rooms, new equipment, and new actions, often using the game interface itself. 1983's Lode Runner was one of the first titles to ship with a level editor, and its designer, Doug Smith, reputedly paid neighborhood children to design levels for the game. That same year the multiplayer dungeon crawl Dandy was released, and it also shipped with a level editor which was documented in the manual. ZZT (1991) is a later game with user-accessible mapping and scripting. Doom (1993) and Doom II (1994) were two of the first games to attract focused game modding activity, and many WAD level files were made for them. One of the reasons was a clear separation between the level files and game engine itself. Half-Life, Quake 3, and many other games have notable mapping tools and communities focusing on user-generated content. Level design for each individual level in a modern game typically starts with concept art, sketches, renderings, and physical models. Once completed, these concepts transform into extensive documentation, environment modeling, and the placing of game specific entities (actors), usually with the aid of a level editor. A level editor may be distributed as a complete stand-alone package, at times, rivaling commercial 3D modelling software. There are various steps involved in laying out a map and these steps may vary dramatically across the many different game genres that exist today.