One reason that I love games is that they often have the raw inspiration of ideas going for them. That and I used to play them in my (more) geeky days in college. "Continuum" was always a game I liked, but never played. Probably because it was a very intimidating game. The board was all of known human history, and you had the ability to travel it at will.
Well not really, things are never that simple. The characters were initiated into the Continuum a society of time travelers. The first thing you get, is the implant that allows you to travel through time and space. As Dr. Who would tell you, you need both as the earth is in constant motion in the universe. If you go back to next year, and don't have the ability to travel through space I certainly hope you can breath in a vacuum.
The other thing you get is the rules of your new society. See there is never a freebie, you get vast powers but are given rules so you don't abuse them. There's a reason. The continuum was created by those grey aliens. Those aliens aren't aliens, they are our descendants, and they get PISSY when their own origin is threatened. So they walled off a part of space time, and basically made it a nature perserve and we are the rangers. If we fail they come in and fix things, but they are not happy campers.
So why do things need to be fixed? Because not every time traveller is a happy member of the continuum. Some are narcissists who think they can change the universe if they try hard enough. This brings up the issue of paradox. Basically, in the game paradox happens when something you know to have happened changes. In cases of paradoxes the universe will "choose" the solution that will cause the least change to the universe as a whole which means that you could very likely become non existent if you get enough paradox or "frag" as they call it. Narcissists always believe they have a plan for dealing with their own paradox, but the Continuum insist they are just deluded individuals. So the fight continues.
To avoid fragging yourself, your future self will often not tell you things, also you are asked to record every journey in time you make in a diary. That's so you can remember, "Oh yeah I have to sometime go back to 1970 and tell myself not open that door." As long as you follow these simple rules you can avoid most grand father paradox.
The game had even more weirdness within like time travelling yeti, and vast empires of rogue time travellers in what we mostly consider prehistory, but you get the idea. I think the base ideas would make the perfect idea for a tv series.
Maybe in time