It is quite abstract. Similar style as the CK II or EU IV.
If I am going to do 3D map, then the local group is the gameworld, if I am going to do this in 2D galaxy can be the gameworld.
Also the average distance between stars is 4ly. In closer to the center they can get as close as about 1ly and further out it gets highly sparse... I don't know what you're doing but it seems that even if you were going for clusters of stars you have layers of star clusters rather than simple 2D, but that's just my thinking
I didn't mean clusters by the most strict definitions. I mean a cluster as an area of stars. Ideally clumps of stars if entire galaxy is observed from the top.
Neither did I. If you're doing a Europa Universalis type game, which I've not played, but your concept seems somewhat in line to one of the ideas I was thinking for a game I've always wanted, just yours would be less to scale and such...
I divide the galaxy into units I call a Lida. 1 Lida = 24TM or roughly 160ish AU. 1 Lida also represents 1 Light Day roughly, which is a much more relevant term than a Light Year. It also just happens to be roughly the diameter of the inside of the heliopause (ie the solar system)
Average distance between stars in this metric is 1,461 Lida, or 1.5 KiloLida.
And the distance from the center of the galaxy to the edge? 50,000 x 365.25. Or 18,262,500 Lida or, 18,262.5 KiloLida.
We can make it a round 20,000 KiloLida
This makes it so you can divide up the galaxy easily into nice blocks AND for movements it relates directly to a day so it's easy to conceptualize movements and such in this unit.
The common size for a sector is 20^3. in this frame it means that it takes 20,000 days for light travel across height, width, or depth of this region and inside this region is roughly 2,197 stars.
This is more than enough to use the way EU uses it's provinces a polities. and you end up on a flat map 1000x1000 clusters or polities.
To include depth, that is 1,826,250 Lida, round and set it KiloLida's that's 2000 KiloLidas and then divided into sectors, that's 100 sectors deep....
So if you add depth you have 1000x1000x100 sectors/polities...or 100 million.
If you start in 1 polity on a flat map you'd have 4 polities to deal with, with 3d map you'd have 6. This is a roughly accurate projection of how much distance between advanced civs there are too, but I don't want to get into that. I see no reason why you wouldn't add in the layers, other than maybe processing or the possibility that player wouldn't keep in mind that there is also a depth component, but I think that's a little too condescending for my tastes... and the processing can be handed by having some sort of scan technology where you can only see a certain number of areas around you or something like that.. since civilizations too far away wouldn't even register with you. You could also use this as a way for the game to balance the challenge as you gain power and conquer those around you it'd be boring if there is no way you could lose so if there was a mechanism so that a new civ could be introduced that rivals yours and this would continue on at bigger and bigger scales that would increase the challenge as need be against the player.