They Came From Space
They came from space ... when no one was looking. No one that is except for you. While all of the Earth's military were wiped out in a sneak attack you managed to scramble into the last tank and got ready to deal the alien scum some payback.
It's time to kick those interstellar punks all the way back to Uranus and beyond. But don't go all trigger happy on us: you need to make your shots count and use your power ups to maximum effect and pick up the ammo they drop.
TIP: try and bag more than one of these critters at a time to get multi-kills and more points! Good luck. We're counting on you!