Some games have physics engines that tell the computer if the object hits a valid polygon. If such a physics engine were to be developed-though this seems like a tough thing to do- trees and other things could get in the way, and if a different unit got in the way, it would take the damage (though probably not allied units). I know glest has something like this because of two things: in glest, you select a unit by clicking on it's model. You can zoom in all the way and click as close to the line as possible, and you will agree with me. Also, if you select a unit that has a unit behind it, you will select both if both are multi-selectable. Clearly, I don't understand everything about this idea, but I think you guys are on to something. Modman likes this idea, too, though he just calls it a physics engine and he has a detailed explanation of what it is. I know there are other games that do not use the selection method of glest, but instead have areas on the ground around the unit that when clicked, select the unit.