"Primary development" refers to the initial or fundamental progress or growth of something. It is the first and most important stage in the development of a person, project, or idea. Full definition
That could be due to the compression of the screenshots themselves, or the fact that the game is still deep within it's primary development cycle. (dualpixels.com)
Responsible for primary development of testing strategies. (glassdoor.com)
This led Gearbox to immediately start work on a sequel, Borderlands 2, and outsource primary development on Colonial Marines to TimeGate Studios, who was developing Section 8: Prejudice at the time. (en.wikipedia.org)