Hi Praetoria.
Which Graviteam game? They have a few.
Steel Fury Kharkov 42 is a WW2 tank simulator
Steel Armor Blaze Of War is a cold war era tank simulator with either M60A3 or T62.
Mius Front is RTS
Operation Star is RTS
They have great physics and great campaigns.
All titles are single player only at his point.
There is a lot of info on all the games on here.
Graviteam make excellent games/sims.
Regards