Perspective can trick the brain into believing the eyes are seeing something they are not.
My two monitors are slightly staggered. The right one is further back, only by a couple inches or so, but it causes the corner on the bottom to appear higher on the one further away, and lower on the top side of that one.
This is because anything lower than the viewer’s eye comes up while anything beneath the viewer’s eye will come down. Everything converges at the eye level.