3D Construction Kit was released on the ZX Spectrum in 1991, and contained a full polygon-based world creation tool.
Whereas frameworks like RSD Game-Maker and Klik & Play attempted to accommodate any genre, communities grew around games like ZZT (later MegaZeux[4]) that permitted such extensive user modification that they essentially became de facto game creation systems.
[citation needed] Whereas earlier game creation systems tend to err on the side of user friendly interfaces,[5] 21st-century systems are often distinguished by extensive scripting languages that attempt to account for every possible user variable.
Some packages, such as Conitec's Gamestudio, include a more comprehensive scripting language under the surface to allow users more leeway in defining their games' behavior.
While most of the mainstream and popular game creation systems may be general-purpose, several exist solely for specific genres.