A persistent world can be achieved by developing and maintaining a single or dynamic instance state of the game world that is shared and viewed by all players around the clock. Quite unlike other types of games, the plot and events in a persistent world game continue to develop even while some of the players are not playing their characters. The real world is persistent, always available and where changes made by a particular person remain even in their absence. In pervasive games, we can speak of physical persistence where the game world is persistent in the physical world.
To give the illusion that the game world is always available, persistent worlds can be simulated. This can be achieved by scheduling when players are allowed to play, around times when the world is offline, or as in the Animal Crossing series, having the game generate events that could have happened during the period of inactivity. Aside from virtual worlds, the simulation of a persistent world is also possible in single player games. In Noctis, players are advised to turn off the game while refueling because it takes so long. In addition, if a player who has landed on a planet stops playing and then after a while resumes, he or she can see visible changes in the sea level or the daytime/nighttime cycle. In Metal Gear Solid 3. If one stops playing long enough during the fight of Snake with "The End", he will die of old age. Another form of simulated persistence has been referred to as pseudo-persistent worlds, in which the game world is shared between computer systems giving the impression of persistence when a user comes in contact with particular system again with which they previously interacted.