hungrytiger has had some interesting ideas, but they require constraining the problem quite a bit.)But this is apparently the kind of problem that *can* be solved for a computer game if you throw enough processing power at it. Check out this Ars Technica review of Achron, an indie game that has been in development for an astoundingly long time and has finally hit alpha. It sounds exceedingly neat: basically a real-time strategy game with time travel, so you can go back and change past events, and have the consequences ripple forward to "now".
The review describes the game as relatively simple, but I suspect that that's a good thing -- if you're going to toss the fourth dimension into a game, it's likely a good idea to simplify the ordinary stuff so that the player's brain doesn't explode. Overall, it sounds extremely neat: really, the first RTS in many years that's actually got me curious enough that I might check it out sometime...
http://jayisgames.com/archives/2007/07/cgdc3_results.php, though doing it with competitive multiplayer is pretty classy.
I've seen time travel be done several ways in LARPs.
Eddie Karat's time travel game (I guess it was called "A Tale of Time Travel") was great fun and worked really well. It takes the easy way out of having the time travel happen pre/postgame, not in game. It still makes your brain hurt.
The other plausible way to do this in LARPs is to use a Groundhog's Day mechanic, where game effectively repeats the same section of time multiple times, with some/all characters retaining memories of the last cycle. This mechanic worked well in Better Luck Next Time (though it was never explained as time travel), and I'm planning on using it in an upcoming game.
I guess the third way of doing it is to mess with the difference between real world and game causality/take advantage of quantum uncertainty. E.g., there's a locked box in game, and people can use a far-past time travel mechanic to change what's inside it up until the point at which it's opened, at which point the timeline becomes fixed. We theoretically had something along these lines in Weird, but it was a minor personal plot that got dropped on the floor (by both GMs and player, I think). This one seems hard to make interesting.
You could probably also do time travel as modules, spending a limited amount of time in a mini-SIK game with set frobs that affect the main time line. Probably could be done well.
Edited at 2010-05-11 06:28 pm (UTC)
The Groundhog Day idea is quite intriguing! I haven't seen it done myself, but yes, I can see that making for an interesting time...