Regions

A region groups rooms and owns behavior for all of them: containing lists members (additive across lines; regions nest), an on every turn clause is a region daemon firing only while the player is in a member room, and after entering it / after leaving it bind to boundary crossings in either direction. leaving exists only on region blocks.

create the Grounds
  a region
  containing the Drive, the Hall

  on every turn while one chance in 6
    phrase night-wind
  end on

  after entering it
    phrase cold-returns
  end after

  after leaving it
    phrase out-of-the-wind
  end after