Galaxy Saving High Adventure - Open Ended Role-Playing
Build for the Science Fiction loving Game Master that wants to build their own universes.
Navigator RPG is a fully 'play it now' game. Pick it up, make a character and start playing, but it is more than that.
Characters follow a life path model. You chose your species, a culture, a profession and then spend a pool of points on skills to customise your character to the way you want them to be.
For the world build GM, the game has common broad species, but the rules for how to create species so they are all balanced in game-play terms. There are common broad-stroke cultures but also the rules for how they are made, so you drill down to any level of detail you like in making your own cultures. The same is true for building professions and even adding skills to the game.
The game as written uses broad descriptions to keep the number of options facing a new player small. There are only a few professions, a few species and so on. This gives you are fairly rules light (Rules medium?) game you can just pick up and play.
It also gives you the potential to refine and add to the game as much detail as you could possibly want.