[MUD-Dev] Mucking about in time

Travis Casey efindel at earthlink.net
Mon Oct 8 14:49:04 New Zealand Daylight Time 2001

Thursday, October 04, 2001, 11:48:09 PM, Eli Stevens wrote:

> Idea, half-baked:

> Store each and every thing that happens in a mud on a stack of
> past events.  Supply an "Undo" and "Redo" feature for each event.
> Allow the last event at any given time to be undone and pushed
> onto another stack, available for redoing.  Doing so would pop it
> off of the redo stack and back onto the undo stack.  In general,
> the redo stack would only be used as temporary storage.

> The mud can accept events that occur at any time.  If the time is
> before the top event on the undo stack, they are popped off,
> undone, moved to the redo stack, the new event is done, pushed
> onto the undo stack, then each even on the redo stack is popped,
> redone, and pushed onto the undo stack as well.

> Presto, you have the ability to change the past.

> Consider this timeline:

>   t-15: Boffo hits Bubba for 4 hp, leaving him with 5 hp.
>   t-10: Bubba hits Boffo, killing Boffo.
>   t-05: Buffy hits Bubba, killing Bubba.
>   t-00: Buffy casts "timeJump -20s flameSmack bubba"

> Time gets unwound at this point, going back to just before Boffo's attack.

>   t-20: Buffy casts "flameSmack Bubba" for 7 hp, leaving Bubba with 2 hp.
>   t-15: Boffo hits Bubba for 4 hp, killing Bubba.
>   t-10: Bubba cannot hit Boffo, he's dead.
>   t-05: Buffy hits Bubba's corpse.
>   t-00: the "timeJump -20s flameSmack bubba" event is discarded.

The main problem that I see is a simple one -- namely, once
different events start happening, characters should be able to make
different decisions.  After all, the conditions under which they
originally made their decisions now never existed, so it doesn't
make sense for them to keep acting as if they did.

In the above example, at t-5 in the second timeline, there's no
reason why Buffy should hit Bubba's corpse -- why would she hit
someone who's already dead?

Now, for a short jump back like this, involving only a few
characters, it may not matter much -- but the longer the jumps back
can be, and the more characters who are involved, the greater the
inconsistencies will become.

For example, if my character goes back in time one week and destroys
a particular store, then going by this system, all events that
involved that store in the last week never happened.  Now,
logically, if someone went to that store five days ago to buy a
sword and found that it wasn't there, they most likely would have
gone and looked for another store, and bought a sword there.
Unfortunately, there's no good way to replay all of those events and
either find out or decide how everyone would have changed their

Even short-term ones can cause problems, if *anything* is allowed.
For example, what happens if Boffo walks into a room, Bubba attacks
him and sends a message to Buffy asking for help, and then Boffo
casts an invisibility spell back in time to just before he walked
into the room?  The spell might prevent Bubba from attacking Boffo,
but what can be done about the fact that Bubba knows that Boffo is
here now?  And what can be done about the fact that Bubba sent a
message to Buffy?

In a paper RPG, these sorts of things can work because the GM can
enforce the principle that characters should not act on
out-of-character knowledge, and because there's a very limited
number of players.  In a mud, I see far too much potential for
problems with messing with the past.  Which isn't to say that I
don't like the idea in principle -- just that I don't see any good
way for it to work in practice.

(You *could* reset the entire mud back to the time of the change,
make the change, then let it start rolling forward from there, but
that has a host of problems in itself -- a major one being that if
the change is more than a few seconds in the past, the set of
players logged in then may be significantly different from the set
logged in now!  The second major one is the players themselves --
even in paper games, where it is technically feasible, this sort of
thing rarely works, because players hate it.  I see the reaction in
a mud being even worse.)

Travis Casey
efindel at earthlink.net

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