Read this to understand the vision of the game:

https://www.p1gaming.net/forum/index.php?threads/design-overview.53330/

You should read at least the link above. If you want to understand more about what we have in mind for our game, you can read more post in the design section of our forum (this is what we use as a GDD):

https://www.p1gaming.net/forum/index.php?forums/design.1341/