Auto-place chains

[DeltaWhy]

I should not have to specify a bounding box for every chain I want to place. I would like to be able to specify a single bounding box and have all chains be placed within that area. Syntax idea:

area 1, 2, 3, 5, 5, 5
repeat do
  # ...
end
chain :foo do
  # ...
end

Algorithm idea: round each chain length up to the nearest power of two, so there is some room to grow earlier chains without needing to replace everything afterwards.