You really have no idea what a symbiotic relationship is. "Helpless without a specific entity" is quite different from "needing assistance." The point is that a fetus is NOT its own entity until it can survive outside of its mother. After that, it's no longer symbiotic. Though babies are certainly quite helpless, the care need not come from a specific person.

Furthermore, where the fuck do you derive "crippled persons should be sacrificed" from "fetuses are not their own entity?" These are two completely different and unrelated statements. You're right that the first one makes no sense. You're wrong that this has anything to do with the abortion debate.

Incidentally, if a crippled person WANTED to be "sacrificed," I believe he should be given the same options -- and counseling -- as a potential mother seeking abortion. I think it's fucking COLD that we force the crippled to burden their families and insurers if they don't want to be. It's why I have a "living will" saying KILL my ass.

Reactive environments (aka deformable terrain) are fairly difficult to achieve. Recent games have begun to attempt this (Red Faction, I believe), but it's going to take a fair amount of reinventing the technology. This has to do with how BSP's (the 3D map of the environment) work, and that the whole thing would have to be rebuilt any time something was changed (imagine having to wait for the map to reload every time you launched a rocket). Most 3D engines rely on being able to pre-compute where everything in the map is, to cut down on rendering time once the action starts (allowing for higher FPS). Maybe someone who played Red Faction can relate how successful they were with addressing these problems. Further adding to the complexity is that now you have to account for building physics. When you blow away that wall, does the roof come down? How much wall needs to be present before the whole thing collapses? How much building has to be added to each map (that you normally wouldn't see) to accomodate possible destruction? All of this greatly increases processing overhead.