[DGD] time travel

[Shentino]

Personally, when dealing with a RNG I'd just settle for dropping a symlink
to /dev/urandom :P

But I agree that history is very bad at making itself amenable to PCG, owing
to the unidirectionality of it.  The arrow of time, if you will.

Otherwise, it would be like looking at a TV screen without a channel tuned
in...nothing but white noise.

Also, considering that the future is derived from the past, and not vice
versa, the past would probably need to be generated first.  This factor also
makes it hard to preserve the present when someone messes with the past.  In
fact, *active* time travellers often count on this.  Passive tourists ala
Chrono Trigger, not so much.