"Gravity" had been in the continuous process of creation ever since Lincoln returned to Earth.
At first, it was just him, Mavis and Camille Victoria working on the project. But Lincoln quickly realized that three people were not enough.
It wasn't a matter of work efficiency - Lincoln didn't care about work efficiency. His original idea was to take it slow, anticipating its completion and launch after "Pacific Rim".
But as they worked on it, they realized that the level of aerospace understanding needed for this game exceeded their knowledge base - much of the knowledge couldn't be acquired on the public Internet.
Of course, Lincoln could create a basic shell, restricting players to only prescribed operations, leading them down a predetermined path.
— For linear plot-oriented games, this approach wouldn't necessarily be problematic.
But Lincoln didn't want it that way.