I've got two scenarios in my sig.
The chess one is for multiplayer. Best as a hotseat one-on-one game (naturally, since its chess
)
The other one is a cool situation: You are a moderately-high tech neutral, who has sucessfully defended their starsystem against all agressors for ages.
Suddenly, your stars grow unstable. Your entire civilization is about to be wiped out, and the only option is to flee with whatever you can carry.
You ulitmate goal is to return and rebuild your ancestral home, no matter what the cost. To ensure it never again suffers the same fate, you must build a ring or sphere world around the crated star as well.
Those glorious plans pale in comparison to the daunting task ahead: survive the destruction of your home in a hostile universe.