Deneb 7 was known to have strange force field surrounding it
that made it impossible to get near planet with year 250 Galactic Era Earth
technology. However, when you were flying past, that field suddenly
reverted and sucked you to the planet.
You find yourself in a strange world, probably touched by superior
technology, where big portion of Earth science is invalid. You
have to learn new rules, rules of this world.
There's deadly radiation that no known shielding works against.
There's alien life, but more surprisingly also some edible
plants just like on Earth.
Radio doesn't work, air doesn't allow flying, some basic Physics
does not apply here.
You struggle to live on this planet, and read Stalker by Strugatski
brothers once more.
Freeciv map generator has big problems generating maps for Alien World.
More often than not, it (thinks it) ends to infinite loop and server aborts.
You can only retry starting game until it succeeds. This problem is made worse
by having more players or smaller world.