Stephen Hawking presents what I take as the textbook interpretation on time travel: i.e. it's impossible due to a cosmic radiation feedback loop. (Into the Universe, S1:E2.) But that's not a very fun interpretation for gameplay :) unless you can make a game of looking back which is more like a "Flashback/Clairvoyance" power than it is a "Time Travel" power.

That said, if you want to eschew Hawking's (nigh irrefutable) views, you should have a look at Continuum. It's a tabletop roleplaying game that "assumes that time travelers (spanners) would eventually evolve their own society, with its own laws, rules, slang, groups, art movements, and the like." It might be of interest to you for setting.

Stephen Hawking presents what I take as the textbook interpretation on time travel: i.e. it's impossible due to a cosmic radiation feedback loop. (Into the Universe, S1:E2.) But that's not a very fun interpretation for gameplay unless you can make a game of looking back which is more like a "Flashback/Clairvoyance" power than it is a "Time Travel" power.

There are other interpretations that allow for it, and get around the feedback loop. I just read one earlier this month by Michio Kaku, but I can't recall the details. To be fair I was mostly skimming that chapter in his book, Physics of the Impossible.

Check out Miegakure.

Unlike what people are saying about time being the fourth dimension, Miegakure has an actual 4th spacial dimension (technically making the game 5-dimensional, if you will).

Stephen Hawking presents what I take as the textbook interpretation on time travel: i.e. it's impossible due to a cosmic radiation feedback loop. (Into the Universe, S1:E2.) But that's not a very fun interpretation for gameplay unless you can make a game of looking back which is more like a "Flashback/Clairvoyance" power than it is a "Time Travel" power.

There are other interpretations that allow for it, and get around the feedback loop. I just read one earlier this month by Michio Kaku, but I can't recall the details. To be fair I was mostly skimming that chapter in his book, Physics of the Impossible.

If only some time travelers came to Mr. Hawking's party, I might believe it. :)

There was a game concept I had worked on with a student a while back. I don't mind sharing it.

The idea was to allow time travel to affect a game, and allow multiplayer in different instances.

Premisis: You are a detective in a crime squad. You are teleported to a city where a bomb just went off. You have the ability to teleport back in time, up to 2 hours from the present track of time. You can bounce around to any 15 minute increment between there. You quickly get the clues you can. 1 thing is that you know the location, but you don't know what the bomb looks like.

Most of the time, you are investigating clues. If you change something in the past, it changes things in the future. Your team can talk to each other if they are in different time zones. once your target a suspect, you can have another team member go back and try to track them, see what they are doing. If they make changes in the world, things might snap out of place in the future. If the police/detective hover too closely to the bomb site, the terrorist might set the bomb somewhere else. Causing the explosion to have happened in a different point of time in the future. I.e. it blows up a building that one of your team in the future happens to be on the second floor. The drop as there is suddenly no second floor and only rubble left.

Never jump times in a car or the street. A car could be their, traffic will change. don't cross the street when someone on your team in the past is about to change something.

The coding premise is that a closed off sand-box city, has 9 stages of time (Time Zone = current time, or a 15 increment up to 2 hours in the past. Initially, the enemy AI/AI's have event times, where they are walking, talking to people, buying things, setting up the device and escaping. Each time zone becomes a mirror of the previous time zone + whatever changes have happened to it. this can include parked cars, locked doors, broken things, accident scenes, etc... When someone in TimeZone 9:15 gets in a car and crashes it, it might take the cops 30 minutes to clean up the scene. which means that any player at timezone 9:30 or 9:45 standing near by, would suddenly see a crashed car their, with police taking care of it.

If a door was kicked in early in the investigation time zones, that door will still be off the hinges in the later time zones.

Its a much different interaction in time than I have seen any other game have.

I don't think it's possible to do this accurately for any significant scale of time.

There are some games that allow you to rewind the latest x seconds or so, prince of persia, braid. And if you "send" the player back in time to accomplish a specific task with a predetermined result you can do that... but to allow the player to arbitrarily go back in time and make arbitrary changes is I think, impossible. This is because in order to accurately determine what effects their actions had requires that you Simulate the entire span of time they skip. Depending on the scale of change the simulation has to run in high resolution... for example, if a player goes back in time 20 years and sets a trap in some random alley and then returns... it nearly impossible for that trap to go undiscovered the entire time, it's also fairly impossible to determine who will find the trap and how. It could be someone finds the trap, and disarms it resulting in no significant time line alteration... or some important figure could spring the trap as a child and die, significantly altering the time line... you wouldn't be able to determine this without simulating the AI for the entire population for the entire 20 years... not to mention the AI would have to be pretty complex for changes to be meaningful.

So, sending the player back to specific points in time, to accomplish specific actions which result in specific results would be possible, but allowing arbitrary time travel making arbitrary modifications for emergent results would not.

it could be done.

if changes in the past change the future, you've created a new "timeline-universe" as mentioned above.

then you have to model the impacts of the new past event on the new future, to figure out what the new future looks like.

like everything else, its all just modeling and simulation.

granted, modeling the impacts of a wide variety of past actions could be a daunting task. <g>

Perhaps remodelling the future doesn't need to be a Real-Time operation. Perhaps it sits on a lower thread, processing the changes to the model, and the player would have a meter indicating how 'caught up' they were in the time shifts happening. then in front of their eyes, see the changes unfold piece by piece. Once the model has determined that a car should be at position 2 instead of position 1, Instead of just 'snapping' into position, it could set some kind of gravity like pull that visually shifts it into place.

Only the characters interacting with multiple times notice the changes. Everyone else is oblivious. You could get away with larger more interactive worlds this way. You could even process time travel the same way, so when you jump into the future by ten minutes, you see things shift around you until you are settled in your new time. Could make for some great visuals.

Remodeling doesn't need to to be intense process if you don't want that, especially for something like a detective.

Because first you "model" the presented/current timeline, then copy it and make a little change to it,

then that change will have certain implications and only calculate those;

in a detective the killer/suspect will be this "little change" and he/she should try to hide it as well,

so the suspect will try to make this real timeline(in which he killed someone) look like the presented timeline

(where the body just dropped from the sky).

Ps i recall some platform game(i think before sands of time) having a whole bunch options( pause/reverse etc.) i think on PS2, but can't remember the title,

anyway it seems to me there was some experimenting with this kind of concept and then it died down.

You could, in theory have a timeline of events scripted out from beginning to end. Then run the timeline forward from where the changes have been made where things that are changed get tracked and those things that are changed by those changes are tracked as well. I think doing it like this would lower the processing and all that, but not sure by how much.