Ooh, I like the idea of gravity mines. If you had "home territory" that you were defending, then you could set up a complex system of gravity mines and have pre-planned "if I shoot at point B, it will pass through point C, D, E and into point A" whereas the enemy would have to learn this through trial an error. It could be argued that the gravity mines would have a limited range effect and that effect could be shielded at greater distances, preventing enemy computers from generating a "map" of the mines. I don't know how this would work in gameplay practice, but it is just an idea