Arcadia is the default world that all my characters and stories fit under. The intention is to offer a kind of base that is flexible for different situations, and simple enough to slot any other characters / scenarios into without feeling out of place.
In the simplest terms, Arcadia is a hyper-realistic virtual reality simulation of Earth - it's such an accurate and high-tech simulation that life within it is completely indistinguishable from life on Earth.
Residents of Arcadia are aware that they are in a virtual environment, and there are perks to this life that wouldn't be possible otherwise, such as fully customisable avatars and the fact that death is not permanent.
Physically, Arcadia is a massive, spherical space station roughly the size of Earth's moon that lies in a heliocentric orbit between Earth and Mars. It is mainly an incredibly powerful supercomputer, thought there are several maintenance facilities on board too.
The station sends out autonomous drones to recharge and replace fuel cells from a Dyson sphere set up around the Sun. These drones are in a constant cycle, making sure that power is constantly supplied and replenished. There are also drones that are sent to mine nearby asteroids for raw materials that can then be brought to the station's onboard foundary for processing. The materials gathered can be used to repair parts of the station itself, or replace any lost drones.
The name Arcadia comes from a name for paradise, as well as "archive" and "ark". The primary purpose of Arcadia is to act as storage for digitised human consciousnesses - after planet Earth became uninhabitable, mankind decided to live a purely digital existence. Arcadia is incredibly powerful, and is also capable of synthesising brand new consciousnesses which are impossible to tell apart from backed up ones - there is no line that can be drawn between "real" and "artificial" entities.
Digital entities reside in Arcadia's hyper-realistic simulation of Earth life, and have no desire or need to interact in a physical means with the space station. The raw computational power of Arcadia is so great, that it is able to simulate many thousands of years for each individual in a matter of seconds. This means that individuals experience a massive amount of time dilation from the physical universe, which is also a means of self-preservation for the station itself - for example, if Arcadia detected an imminent threat from outside, it would have millennia to calculate a solution to the problem.
Arcadia's virtual environment is that of planet Earth in the late 20th century. Geographically, the architecture is 100% accurate to the time period, and the scale of the planet is 1:1. However, in order to stop overpopulation, there exist several instances of each world that individuals can travel between if needed. Accuracy to the time period in a historical sense is not of importance, so there are many "quality of life" updates from future centuries that exist in the virtual environment.
Besides the main world, individuals are free to set up and maintain their own recreational worlds. These are usually roleplaying environments of some kind, allowing an immersive experience using Arcadia's technology in different contexts.
People in Arcadia experience an accurate simulation of Earth life - for better or for worse. In Arcadia, people age, get tired, hungry, sick, injured and can die. Therefore, people work to earn money in order to maintain their own care needs. The main economical difference in Arcadia is that money can be used for things that would be impossible in a physical space, like being able to alter one's avatar in any way according to the individual's taste. Due to the flexibility with avatars, the physical limits of avatars can be a lot more resilient than physical bodies. Any injuries that occur besides death can be quickly fixed simply by paying to "refresh" the avatar.
Individuals can breed within Arcadia, though the physical constraints of gender and sex are no longer important. Two individuals can consent to have a child, and then the system will take into account code from both individuals and randomly generate a new consciousness to be gestated within the chosen partner's body. Any children born this way age in the regular, expected way - timeskips to adulthood aren't something that is available!
When somebody dies in Arcadia, they have the option to pay a large sum to respawn, and can choose the age at which they do so. If the sum is too large to pay, there are several other options: The first is to take the sum as a debt into the next life that must be repaid - this option is not available if there is still a debt upon a person's death. If there is an existing debt or the person doesn't wish to take a debt to respawn, the individual must wait in a form of stasis for a set amount of time before respawning - this is usually a year or so at the minimum. At any point, someone still living can choose to pay off someone's death fee and have them respawn immediately.
There are still politics, crime and wars within Arcadia, and all these things are run without interference from the computer, as they provide an "accurate" simulation of Earth life. Military and law enforcement agencies are present as one may expect, but being a fully digital space has also allowed for individuals to create malicious entities that exploit the digital domain. As such, there are branches of defense dedicated to combating these threats too, destroying maliciously coded entities, restoring order to any hacked spaces, and apprehending those who create these issues.