A Massively Multiplayer Online game (MMO) is a feature that can be developed at the R&D lab. In order to gain access to MMO, the player must first develop Internet, which unlocks both MMO and Codename: GRID.
After MMO is developed, MMO support for engine will be available for research by the player or his/her employees. The player must then develop an engine with MMO support to make MMO Games.Conditions for required researches for MMO are at Research Unlocks page.
Once a MMO is made, it will kind of work like a custom console, with maintenance (Although a different kind) needed, however you may constantly make money. As time goes on, you will steadily make less and less money, while maintenance remains the same. If you don't feel like pulling down a MMO by right clicking the tab and removing it, you can try making expansion packs to make it popular again.
After releasing it, you can research expansions and then develop them. Although not a complete game, it can improve an MMO and raise its income. It can be developed just like any other game
- If you cannot steadily produce the expansions before the maintenance costs rise, it is encouraged to take the MMO off the market. To do so, left-click the MMO's Net Income/Net Loss Bar Graph and select "Take off market."