Traveller
Traveller has been around for almost as long as D&D. It arrived as a stripped down set of SciFi rules with streamlined character design and straightforward combat rules. Character advancement was only sketched out, combat often ended badly and there was a distinct shortage of aliens.
There haven’t been a great many changes since then, as Classic Traveller remained the version of choice until the relatively recent release of Mongoose Traveller, (which keeps much of the minimal approach of the original booklets).

Mongoose Traveller Core Rulebook
Over the years various supplements and add-ons have appeared for Traveller but these tend to be more about kick-starting a setting or a series of scenarios rather than multi-volume ‘battle game’ campaigns.
The simplicity of Traveller’s rules encourages players and GMs to use their own imaginations to ‘populate’ and ‘live’ the setting. The same core simplicity also challenges GMs to fill the gaps in the rules with patches and hacks. Need an alien, invent an alien; need nanotechnology, come up with a set of nano-devices and sell them to players for a small fortune.
By asking players to be wary of combat, to explore large systems and to live the character instead of the class, Traveller often delivers open-ended roleplaying and co-operative play. Plot driven adventures featuring powerful syndicates, industrial espionage and corporate intrigue are typical backdrops developed by GMs and players.

Book 2: High Guard (Traveller)
In other words, ‘rules light’ players and GMs find themselves in the ‘driving seat’ in terms of directing the narrative, defining the setting, planning missions and running play. Under these conditions the written rules serve more as a framework for players to build on than an instruction set.
When tabletop RPG rules are treated as a framework the interactions between players often change. Instead of focusing on the GM and a Q&A format, players and the GM engage in more fluid narratives and complex roleplaying through exchanging and building on, (or ’scaffolding’), each other’s ideas and options. Under these circumstances players use many skills, including critical thinking, collaborative planning and frequent decision making.
Players usually enjoy more open-ended gameplay, as adventures become less predictable and more personally involving. However, players are suddenly being encouraged to take part in a style of play comparable to stepping onto the set of an interactive movie. Instead of simply looking after their own character, players are asked to become part producer, part director, part scriptwriter and part leading actress/ actor.

Traveller: Spinward Marches (The Third Imperium)
Some tabletop players have neither the time nor the energy to shape ‘rules light’ play on a regular basis. So it’s worth considering more ‘off the shelf’ options if your games are played after a long day at work. Groups where most of the players enjoy sitting back and letting a campaign pack flow over them may also prefer to stick to the ’shrink wrap’ option. A Mongoose Traveller setting like the Spinward Marches has lots of helpful ideas to offer, but there’s still work to be done before a campaign gets started.
Overall, Traveller has less support and fewer players than leading ‘battle games’. This seems to be because Traveller’s players and GMs have to ‘work’ harder during play and a majority of tabletop RPG players prefer fantasy settings. For those prepared to try a SciFi setting, (and play shorter, more intense games), Traveller offers open-ended, roleplaying-focused gameplay. Traveller is, therefore, ideally suited to players looking to stretch their imaginations and use shared gaming to get the most out of roleplaying.
