Collision between player and enemy

Hi,

How are collisions done between player and enemies?

So I have a spider as the enemy which is two times larger than the player. So if the player creeps he should go under the spider.

The spider has a dynamic box which is green in the image. I thought of adding invisible cubes parented only to the bones (legs of spider) which have the object type sensor. If the player collides with them he does whatsoever for an action.

http://www.conspicuous.ch/blend_img/spider_sensor.jpg

Or is there another approach for that?

Thanks in advance


MAGIC FLIGHT