Game director Keiichiro Toyama proposed Gravite to Sony in April 2008 as a retail “gravity action” title aimed at the core audience, which would be extended through post-release, downloadable episodes.
Gravite was developed for PlayStation 3 through 2009 and 2010. The first concept video created for internal purposes was shown in January 2009. An imageboard presentation was put together in January 2010.
Of course, as any game’s development goes, character’s change. Here’s a look at some of the earlier to final designs for Kat and Raven:
And some town and civilian artwork:
The article does not mention why the game switched development to PlayStation Vita, but we can only assume that budget, or having a new IP ready for new hardware, played an important role.