Play advances through actions. Actions are not large-scale tasks like "exploring Hindustan" (or Hindostan, as Grenville spells it) but the little individual motions and impulses which make that up: "going east", "climbing the temple stairs", "examining the ceiling" and so on.
Like the Index, the Skein for a project is automatically maintained: it remembers every command typed in, not only in the current translated version but in all previous ones.