The true source for Stefan's spiral into madness is up for debate — the pills he's taking? The P.A.C. influence? A lingering curse from Jerome F. Davies (Jeff Minter)? — but it seems to be sparked by an obsession with the shape of the flowchart that helps him organise the story of his game. After a few scenes, the thinly-lined chart begins to morph into more of a glyph, made up of thicker lines (which you can see above). What's more, is that it very closely resembles the symbols drawn on the masks of the attackers in Black Mirror's "White Bear" episode.