Why without the relativity thing? I think time dilation would be the most interesting aspect here. She could be circulating around the earth, at a speed near the speed of light. She would feel that only a day has passed, while it could be a month for the observer on the earth.[/quote]leon wrote: Kind of, but without the whole relativity thing. Mars is in an interesting place for a story like this - between 4 and 20 light-minutes away. Double that for the round-trip time, and add another few minutes for recording the reply, and the delay between messages could be anywhere between 10 minutes and an hour. That's long enough that the light-time factors into things - but it means one could pull off a playthrough in an evening, or at least a weekend day.
A couple of things.
Scientifically, solar system escape velocity is 0.00014% of light. When moving at that speed, relativity slows time down by 0.0000001% or so. That's hardly noticeable, at least according to human timescales. By the time your perceived time is half of that of an earth-based observer, you're moving at 86.6% of light speed. Long before relativity is substantial, you've flung yourself out of the solar system.
You can come up with Mazer Rakham-ish solutions in which you boost out and come back again - but it's tough to think of a compelling reason for this.
Double Star, along with Voices of a Distant Star and other works, pointed out a problem with this - at a high percentage of c, communication could become difficult to impossible, as the thinking of the traveler slows down to the point where it takes him a long time to reply to a message.
From a games perspective, Mars is interesting because it's close enough that someone could plausibly carry on a long distance relationship with a character there. People are talking about reducing the price of Mars travel to the point where upper-middle class people could afford to make the trip. (See Elon Musk's most recent National Press Club talk.) This makes a VN somewhat interesting.
Plus, Mars is unique among the planets insofar as there is a ton of high-quality photography of it, all in the public domain. That could help in illustrating a game.
Mars is far enough that one could use the time-based mechanic to create a game about isolation - but it's close enough that such a game could have a happy ending.