I walk very slowly around the room for an hour, and then I go outside and walk in the street. When I am startled, I feel strange: a kind of vertiginous tug back into black glass dark. Twice, I have to stop—once when a vehicle sprays water into the air and the pattern of light and refraction is so complex that I feel myself bubble and bloat in the wrong direction inside; and once when someone talks to me, loudly and suddenly. I turn and run away, and then I realise that I can run, and jump, and shout and sing.