You were a God of some sorts in his world, but in your world, you were just an ordinary teenager wanting to play the new Black Mirror interactive episode. You boot it up, play some routes like an ordinary person, make Stefan do some stuff, until he starts to yell upwards, screaming at supposedly nothing.

“Who are you?! Whoever you are, give me a sign, just give me a fucking sign!”

You had an option to actually tell him what you were doing to him.