Here is a cool idea for time travel video game:
Story
A famous art peice was stolen by time travellers and you work for the temporal police. Your time sensors don't work that well, so you can only pinpoint the crime to a day or so and you don't know exactly where the crooks are hiding. So your character is sent though time and they must catch the bad guys by finding clues in the past. You use a time travel sute to go though time.
I would love it if the game took place in old Venice.
Gameplay
It would be a classic first person point and click Myst like adventure game. You would have an artificial being as a companion who would say comments and clues to help you.
Your time travel sut would make an avatar of a class of person from the past. It starts out very low class and as the need rises for a higher class of person, new avatars are unlocked. Avatars could be customized. You can also change them depending on the sitawastoin.
The Cycle
The game-play would revolve around a "cycle". Each "cycle" starts a day and half from when the theft occurs. Things happen at cutrun times of the day, for example a city official you need to talk takes a walk every day at around 5:00 AM.
To reduce complexity for the programmers and the players cycles would only be a day and a half. Then your artificial companion send you back to the start of the cycle.(he would explain what's happening the first couple of times). Time moves forward in real time but there is a "time wheel"(explained in the next section) you can use to travel forwards and backwards in time.
The reason cycles move in real time(but only when the game runs) is to give plenty of time for people to figure out what do without time pressure. For the cycle to expire natural you would have to keep your computer running with the game on for a day and a half.
Time Wheel
The Time Wheel advances slowly as time advances.(which as I said is real time) As you get closer to the end of the cycle the wheel turns from green to yellow, orginge to red. But your a time traveler, so you can move the wheel to rewind or fast foword time but only within the bounds of the cyles.
So if you arrive at a bar and say "I want to speak to Jacob" and the bartender says "He was here an hour ago but has gone home now", you can solve that mini-puzzle but rewinding time an hour.
You turn inviable when you move the wheel and if your around people they will react like you appeared or disappeared in front of them.
Another example is a vishush dog blocking your path and time moving backwards or forwards till when the dog is not there.
If real time is too slow you might also be able to speed up the speed of time with a 2nd dial. This would make everything faster including people talking like chipmunks if too fast.
Death
You can not die in the game but you can brush with death and your artificial companion will rewind time for you right before you die and scold you.
Classes
As I said you will gain avatars of different social classes throught the adventure. You can switch between them at different points. Like with the time wheel this will cause people to react.
Your class avatar would be visible in the hud.
Stir
"Stir" like the phrase "that is causing quite a stir" is the messure of how much coes you create. Changing class or moving though time(remember this makes you invisible) in from of people raises your "Stir". Sovling puzzles in as inconspicuousness a manner as possible(most out of site, lest sound and lowest class) will reduce the amount of "Stir" you gain.
So people don't fert about "Stir" your boss would say "complete the mission at all costs" or something like that and you would never loose if "Stir" gets too high.
At the end of the game your "Stir" is your high score and the lower the better. This gives an instenvie to reply the game.
There would be a few hidden areas where people never go where you can time travel or change class without people noticing.
Inventory
Would work like a lot of point and click adventure games. You can get items from the future and use them in the past but this can cause more "Stir" if you for example drink a bear in the bar before the bartender has had time to brew any.
Also you keep all inventory even if the cycle restarts or you go back in time. That way you don't have to remember where things are when going though time. This is explained in the story with "techno babble".
Conversations
Would be a dialog tree.
Linux release
I don't know what platform the game would be on, other then Windows. There would also be a native Linux release as I like that platform.