The Da Vinci eggs probably didn't actually make things happen. I'm not entirely certain, but I don't think that causing an action in a video game requires a texture on an object, and no beam is necessary to add an extra part to a function (I speak specifically of the Da Vinci eggs here; the landmines could easily have been programmed to activate on their own when a player got near, without resorting to a separate unit in a distant tower shooting them in order to activate them). My point is that proper use of Occam's Razor would take out the unnecessary parts to make a simpler, ie cheaper, function that does the same thing. Unless, of course, the designer left the extra units to be found. The Da Vinci grid in ODST seemed to have no function, either. This could be the Da Vinci secret of Reach, wrapped up in a new texture.
