HitDetection Theory?

Okay, this is more of a question asking for how I should approach this when I get to this rather than asking for coding help.

  1. My game is a click shoot style game. I want the enemies to loose more Hitpoints when I shoot them in the head then when shot in torso, or limbs. Now, how does one do this, what concept should I study so I don’t have to ask so many questions when I come to this? Obviously I could have a variable called “hitpoints” for the enemy, and “damage” for the bullet, and ad/multiply/divide them according to where hit, but how do I get the head, torso and limbs to each be separate parts that can be hit?

  2. Once I get the multiple boxes that would make up the hit detection, could I simply create a new layer and “skin” graphics over them?

  3. Currently I’m using hitDetectObject in my click shoot game. This is fine but it seems that this draws a large box around the enemies shape, now I hope to get the hit detection to be location specific, and I want to skin graphics over this, but I want the hit detection to be based on the boxes and not the skinned over graphics as this would probably be to processor intensive. How could I more accurately and reasonably test hits?