This has got to be one cool optical illusion. Don’t worry there is no screaming voice or a ghost that would suddenly appear.
Just keep staring at the screen until the instructions on the screen ask you not to start any more. Full size the video and stare directly at the center.
Then when you are to move away, suddenly look away and focus on somethin nearby you. Preferably the face of someone sitting nearby and then you will know what I am talking about.
Totally work safe.