Game creation system

A game-creation system, or GCS, is a program released which is designed to enable the user to create a computer game using the system. Often, but not always, the game-creation system is itself a game which gives players such control over how a game's "add-ons" may be modified or edited (without the game being "modded") that the add-ons created go beyond additional "maps" or "levels" and get into the category of being additional "worlds," "quests" or "games" within the game. The most prominent example of a GCS that is not itself a game is Game Maker. Prominent examples of game-creation systems which are themselves games include ZZT and MegaZeux. Users of one GCS often cross-over to another or use multiple systems at once (this often occurs with ZZT and MegaZeux.)