Three Days Till Dawn
Traveller is a science fiction roleplaying game. It’s reasonably “hard” science fiction in that, apart from the staples such as FTL travel, artificial gravity, safe (mostly) cryogenics, a little psionics, etc., it’s meant to be “realistic” and somewhat low-tech. If you start with Firefly and shy assiduously away from Star Wars and Star Trek, you won’t go far wrong.
The name “Traveller” is a reference to the default occupation of player characters, which is to move around and between stellar systems seeking adventure and profit. There are no character “levels” per se, just goals such as getting out of debt (a common one), exploring, buying a better ship, righting wrongs, etc. Fighting is of course a possibility in any of these, but it’s to be treated with care as it has the potential to be exceedingly deadly.
It is so deadly that Traveller is known as the game in which it is possible for your character to die during the creation process. In fact, in the Mongoose ruleset I’m using, it would be unusual for a character to die outright during generation, and even then a player can choose to go into “medical debt” to keep it alive, creating in the process a rather interesting roleplaying hook for that character.
Most characters will not reach that extreme, but all characters will experience events throughout their career that modify their skills and characteristics, or perhaps just their life story. The rules are written with the assumption that the character creation process is a cooperative one, with other PCs taking on the roles of Contacts, Allies, Rivals, Enemies or even family that might arise during a character’s career, and characters can receive bonus skills for entering into such connections. This, however, is intended to be mere frosting to the cake1 of an interesting and interconnected group of travellers.
1 Or the other way around, if you’re more of a frosting person.