Question how to make the spotlight always direct toward the center(the target image)

I am making an AR project. And I want the keep the spotlight directing to the center while I move it by touching and move on the screen. The diagram shows that right now when I move the light, they are all directing in the same direction, as the pink sketches show. However, I want them to have an effect shown in the green sketches, which is always directing to the center.