I won't argue that G/Sata Ball isn't a lot of work (I highly suspect it was since they have to design the game/rules, code all the game rules, create the level design/playing field, all the art assets, any/all special effects, add a scoring system, create a leaderboard/ranking/statistics system). All of that takes a decent amount of work, but the foundation of simply adding FPS to the scope of the game and even zero-g combat isn't much more than reusing the zero-g ship combat, the only difference is that the "ship" is you and your "thrusters" are your weapons and/or any rocket packs/push/pull mechanics, and that is my point, in that it really isn't a lot of extra work at the fundamental level, especially if they applied proper object oriented design where-in everything would already inherit most of the previous work done for ships. The only slight addition that might make things a little more complex is the changing center of gravity for a person's model when moving/grabbing/carrying an object/etc., but again, that is a very simple calculation.