I am an eight-year-old girl, standing near-naked in a room full of strangers. As the room spins and zooms upon me and people glide around me, I clock my features. I don't look eight. I look like a grey Barbie doll, complete with cleavage and bare feet locked uncomfortably in the high-heel position. I have a large block head that resembles a grey marshmallow. I'm in the world of Roblox, where block-like avatars transform themselves to explore a universe comprising millions of user-generated games.