A simulation video game describes a diverse super-category of video games, generally designed to closely simulate real world activities. A simulation game attempts to copy various activities from real life in the form of a game for various purposes such as training, analysis, prediction, or simply entertainment. Usually there are no strictly defined goals in the game, with the player instead allowed to control a character or environment freely. Well-known examples are war games, business games, and role play simulation. From three basic types of strategic, planning, and learning exercises: games, simulations, and case studies, a number of hybrids may be considered, including simulation games that are used as case studies. Comparisons of the merits of simulation games versus other teaching techniques have been carried out by many researchers and a number of comprehensive reviews have been published. Subgenres = Construction and management simulation =Construction and management simulation (CMS) is a type of simulation game in which players build, expand or manage fictional communities or projects with limited resources. Strategy games sometimes incorporate CMS aspects into their game economy, as players must manage resources while expanding their projects. Pure CMS games differ from strategy games in that 'the player's goal is not to defeat an enemy, but to build something within the context of an ongoing process. ' Games in this category are sometimes also called 'management games'. = Life simulation =Life simulation games (or artificial life games) are a subgenre of simulation video games in which the player lives or controls one or more artificial lifeforms. A life simulation game can revolve around 'individuals and relationships, or it could be a simulation of an ecosystem'. Social simulation games are one of its subgenres.