Science Fiction roleplaying games usually focus on the future, and usually use technology as the source of wonder, where a
Fantasy game would use magic. Aliens, spaceships, psionics, laser blasts, and other planets all have their place here, though not all games will use all of these. The first Science Fiction roleplaying game (the first roleplaying game at all that was not a medieval fantasy) was GDW's
Traveller.