IT'S Thursday night at the University of California, Berkeley and Alan Feng, a physics major, is lecturing a roomful of students. He's using a video of an old battle to describe Game Theory. Feng, 20, betrays no feelings about the emotional cost of war. His only concern is the efficiency of the formations and the movement of resources. In fact, Feng's no professor and these are no ordinary soldiers: they're ugly, insect-like aliens fighting human-like aliens.