currency-based economies. Shortly after, in 2000, Habbo launched and grew to become one of the most popular and longest running virtual worlds with millions of users around the world. Virtual world concepts Definitions for a "virtual world" include: "A virtual world is something with the following characteristics: It operates using an underlying automated rule set—its physics; Each player represents an individual "in" the virtual world-that player’s character; Interaction with the world takes place in real time—if you do something, it happens pretty much when you do it; The world is shared-other people can play in the same world at the same time as you; The world is persistent-it’s still there when you’re not; It’s not the real world", by Richard Bartle in 2015 "A simulated environment where many agents can virtually interact with each other, act and react to things, phenomena and the environment; agents can be zero or many human(s), each represented by many entities called a virtual self (an avatar), or many software agents; all action/reaction/interaction must happen in a real-time shared spatiotemporal nonpausable virtual environment; the environment may consist of many data spaces, but the collection of data spaces should constitute a shared data space, one persistent shard", by Nevelsteen in 2018 There is no generally accepted definition of virtual world, but they do require that the world be persistent; in other words, the world must continue to exist even after a user exits the world, and user-made changes to the world should be preserved. While the interaction with other participants is done in real-time, time consistency is not always maintained in online virtual worlds. For example, EverQuest time passes faster than real-time despite using the same calendar and time units to present game time. As virtual world is a general term, the virtual environment supports varying degrees of play and gaming. Some uses of the term include Massively multiplayer online games (MMOGs) games in which a large number of players interact within a virtual world. The concept of MMO has spread to other game types such as sports, real-time strategy and others. The persistence criterion is the only criterion that separates virtual worlds from video games, meaning that some MMO versions of RTS and FPS games resemble virtual worlds; Destiny is a video game that is such a pseudo virtual world. Emerging concepts include basing the terrain of such games on real satellite photos, such as