Face recognition

You guys probably have seen the face recognition software where the app pastes dog features or modifies a person’s face dynamically.
It is great and face warping probably is a technical feat, I’ve never seen anything like it.

My question is, anyone knows how hard it is to do?

All I want to do is software that calculates what area is a face and make objects drawn over it to move as the face moves in the picture.
Plainly put, I want to make a game where you have to pop zits that appear in your face, kind of like a whack-a-mole thing.
I believe it would be easier to make than radically warping a person’s face like I’ve seen. Just pasting features…
I don’t know where to start…

I once did some research in this space for a university course.
I suggest you look into using open CV, i think it’ll get you where you want without too much work. I vaguely remember an example using this tool where it actually worked out all the vertices on your face which you could theoretically take to skew an image and analyse geometrically for the placement of overlays.