Designing for Extensibility

Something that I did unconsciously with Gaslands was designing the game system in a way that gave me a lot of design space to explore beyond the game’s initial scope. 

This turned out to be really important as the game grew. During the development of A Billion Suns, I spent some time considering what it means to design for extensibility, to ensure I give myself a fighting chance of giving A Billion Suns the same expandability.

In Gaslands, the vehicle and team construction rules, and the scenarios, provided easily-accessible design space to explore. With the help of my awesome development & playtesting group, Joe, Phil, Jay and Glenn, I expanded and explored a range of new vehicle classes, weapons, perks, sponsors and scenarios in the Gaslands: Time Extended! downloadable PDF series. These PDFs ultimately led to the revised and expanded hardback edition.

As I’ve made design decisions for A Billion Suns, I have been more actively looking for opportunities to build extensibility (and therefore hopefully longevity) into the system. I need some juicy hooks on which I can hang additional or alternative content after the game’s release.

Work For Hire

Contracts were the first place I attempted to build in extensibility. From the start, I imagined having “packs” of missions that created different feeling science fiction experiences. As I deliberately choose to avoid the “scenario” structuring device. I had used the “scenario” as my key fun-structuring device in Gaslands. I wanted to do something different with A Billion Suns. Taking a leaf out of Malifaux’s book (probably the miniatures wargame I am most inspired and delighted by) I wanted to create an buffet of tactical objectives that could be combined in any combination to create a unique feeling game. 

As an aside, with just the 12 core systems contracts, choosing 3 contracts each game provides 220 unique game set-ups, and that’s before you even consider the number of players or the systems administrator’s setup choices. Creating new contract sets, either stand-alone or which can be mixed in with the Core Systems contracts, offers a lot of design space for creating new interstellar stories. They can be used to create narratives, and provide pacing for the games. Many of the Core Systems contracts are “jobs”, but they can also be objective-based missions, kill missions, movement-based missions, and all sorts of other activities. I’m convinced I’ve only scratched the surface of the contracts design space.

Tech Trees Arborists

Competitive Advantages are the second place I deliberately created a framework for extensibility. The competitive advantages are organised into sort of “tech trees” but the compatibility is “inwards”, rather than outwards, providing unlimited space for growth. I’m pretty happy with this design choice, as what I realised was that if Competitive Advantage #1 said “unlocks access to #2 and #3”, the system breaks when I add #4 in a later expansion. 

Instead, competitive advantages have pre-requisites, so they say “requires you already have #1”. This means I can expand the tree any time I like without changing any of the previous leaves, I can easily add whole new classes of competitive advantage and I can flexibly graft new branches onto any part of the tree.


The last area that I wrestled with, but ultimately had to ignore for the purpose of the initial rulebook, is the idea of customisable ship classes. The statistics of each ship class is fixed, and individual ships don’t have much scope for customisation. This is fundamentally different to Gaslands, but reflects the fact that list building is not really an ABS activity.

Interesting, as I have begun to draft the first expansions for A Billion Suns, the ship classes have proven to be a very nature design space. Because the ship classes (and their weapon load-outs) are fixed, providing new ship classes does actually provide interesting new options. So ship classes aren’t customisable, but the list of ship classes could be bigger, or (perhaps better), the á la menu of ship classes could be swapped out for a different one in some cases, to provide new play experiences without paralysing the players with choice when they go to jump a battlegroup in.

Pirates, Prospectors and Rebels

Taking all this together, it is easy to imagine that an interesting shape for an ABS expansion would be a themed pack containing a new contract set with a handful of new ship classes and some themed competitive advantages. Pirates, prospectors, black ops, rebellion, alien invasion, AI uprising – I’m pretty confident the system has rich enough hooks on which to build expansions to tell any kind of science-fiction story.