Unitpear

So, I always catch myself nodding my camera in response to questions asked by NPCs in Half-Life 2. So I thought, what if in the next Half-Life game, this is turned into a mechanic to actually speak to other NPCs? So, let's say an NPC asks you a yes or no question. If you nod your camera up and down or left and right, it will trigger different dialogue and events. All without having to have Gordon speak at all, as well as giving the player control of the game still. The reason I post this in modding is because I've never actually seen anyone implement anything like this, and I would really love to see something like this.