ok, so it was a pc game. I remember playing it maybe 10-12 years ago. It took place in space. the first level was on the moon, you drove around in all the different space vehicles (tanks, howitzers, walkers) and had to fight the enemy. the plot was that the U.S and the Russians moved armies into space during the cold war to fight each other (or at the very least thats what I can remember) you could eject and jump out of your vehicle if it got destroyed and you could run around the surface.