As this topic progresses sections will naturally need to be revised. The latest and "official" version will always be the Google Doc. If you open the google doc I've set it so that anyone can comment on it directly, or you can post here of course. I'll make sure that all major updates get posted here as well, but more minor edits of wording and organization will probably not all get posted into this thread.
Introduction
What Is a Roleplaying Game?
Interregnum is a table-top roleplaying game set in a science fiction universe where galactic society has relatively recently collapsed, and it is at a "dark age" point in the rise and fall cycle of great galactic empires. One person is the Gamemaster (GM) and manages the setting information and non-player characters (NPCs). Everyone else in the group is a Player and controls a character of their own (a PC) within the game universe. The players say what they want their characters to do, and then the GM determines what happens using both the rules of the game (for situations that the rules cover) and an element of judgement (when players go outside what the rules anticipate). Players are highly encouraged to provide suggestions for outcomes when the GM isn't sure what to do, and the GM should work with the players in this regard so that the result is a fun and exciting story that unfolds.
The player group (often called a crew, party, gang, band, etc) generally has much less in the way of resources than they would like to have, and they are less averse to the dangers involved in various asymmetric means of attaining more resources quickly than the average person. In other words, you hunt for lost treasures in dangerous places, you commit stealthy crimes against powerful organizations in hopes of a big score, or strike out to some new frontier and carve out a piece of the universe for yourself. Basically, you're a daring space adventurer, because just having a day job is pretty boring. The term "murderhobo" would not be misplaced.
Introductory Dice Mechanics
In Interregnum, when a character wants to something and the results are uncertain they roll a Dicepool. This is some number of six-sided dice. The exact number is based on the situation, generally one of your stats plus one of your skills, but sometimes with extra modifiers too. Once the dice are rolled count the number of dice that show a 5 or a 6, these are Hits and any other dice are Misses. Depending on the difficulty of the situation you'll need a minimum number of hits to succeed at all, this is the Threshold. Any hits in excess of the threshold needed are Net Hits, and they can often get you a bonus (such as extra damage on an attack, or performing an extended task faster than normal). Sometimes your roll won't have a specific threshold, and it will instead set the threshold for the opposition's roll (eg: your Stealth roll vs their Perception roll).
If you aren't under a lot of pressure you can choose to Buy Hits, and not roll at all. Instead, for every four full dice you would have had in your pool, you just get 1 automatic hit. This gets you less hits than your average (normally you average 1 hit per 3 dice), but it eliminates the chance of an unlucky roll causing an unexpected failure with a routine task.
Many more details are provided in later chapters, but that's enough to get you familiar with the core mechanic for now.
The Science in Science Fiction
Broadly speaking, Interregnum is a science fiction setting that's intended to be a little more like a wild space opera than like a hard sci fi sort of thing. More like Flash Gordon or Farscape than like Gattaca or Contact. There's some old west sensibility as well, so maybe think Firefly too; a wagon train to the stars, they call it. Foundation obviously has to be mentioned as a setting inspiration, but the story focus isn't with the people from tiny bits of old power that are left here and there, it's with the people living among the relatively "collapsed" segments of the galaxy. Lastly, there's aliens. Lots and lots of aliens. Samurai Jack levels of all sorts of aliens.
Science Fiction is a very broad genre, with various conventions that might be in play from series to series. The main thing that sets science fiction stories apart from each other and apart from other genres is a consideration of what sorts of new technologies exist compared to the real world, and how those technologies impact the lives of people in the setting. Naturally, before we can discuss too much of the game, it's best to get an overview of those technologies.
The Hyperlane Network: Faster Than Light
The Hyperlane Network is a series of paths between the stars that connect up the millions and millions of star systems within the galaxy. Ships equipped with a "hyperlight drive" can enter into a hyperlane and travel along it to move to the next star system. The exact name of the system varies from world to world, "hyperspace engines", "ftl drive", "hyperdrive", etc are all common synonyms. As one might imagine, there are a number of significant limitations on this system.
The first drawback is the classic "strong gravity interferes with hyperspace". You can't enter or exit hyperspace too close to a strong external gravity source. This mostly means planets, but specialized ships can cast an interdiction field around themselves as well. Hyperdrives are designed with all sorts of safeguards to prevent problems under normal circumstances, and attempts to bypass these safeguards for any reason risk heavy damage to the ship's systems (power overloads, engine burnout, etc), violent turbulence within the ship (which can itself be fatal), and/or instant death as the entire ship is vaporized.
The next limitation is that hyperspace itself is very perilous, and ships must move along a known hyperspace route as they travel between systems. Over time the lanes shift and twist slightly, so to speak, and using old star charts can get you shunted into deep space, stranded between stars. Most interstellar travel takes place along well known routes that people keep up to date on. Discovering lost hyper routes is a rare thing, but such information can make a person very rich if sold to the right people. It is unknown if the hyperlanes were originally created by some ancient society, or simply mapped by that society. The physics suggest that it should be possible to create an entirely new hyperroute out of nothing given the right circumstances, but the predicted energy levels required to do so exceed the output of several stars combined. All that's known for sure is that the Standard Template Library plans of how to build a hyperdrive also include an old (and now very out of date) starchart that gives routes connecting over 7 billion habitable planets. Modern starcharts are usually iterations off of this ancient version, and maps to places outside the STL map are jealously guarded secrets.
And finally, while hypertravel is very fast compared to sub-light speeds, it's still unfortunately slow on a galactic scale. A ship's hyperdrive rating is some positive number that's generally in the range of 50 to 150, and this is the ship's speed in light years per hour. Ships that can devote proportionally more space over to engines can move faster, but larger ships also move slower simply because of their mass. While 100 light years per hour might seems ludicrously fast, on a galactic scale that's actually not too much. For example, the Milky Way galaxy is 100,000 light years across (or possibly more, it's hard to tell from the inside); even with good a good set of engines on your ship it would take weeks to make it all the way from one end to the other. Truly, space is a vast ocean.
this section cut to improve the tone
Hyperwave Radio: Shout Through the Stars
They say nothing beats the speed of bad news, and with a hyperwave radio at hand, they're right. In addition to hyperdrives, the other most common hyperspace technology is the hyperwave radio. It lets you broadcast signals instantly across the galaxy. A given hyper-transceiver can send a signal out to a given range based on the power available. A hand device works anywhere within a single system, a backpack-sized device works out to a few dozen light years, and one built into a starship can work out to hundreds or even thousands of light years away. If range above that is needed, people usually prefer the cheap option of simply setting up a network of re-transmitters, rather than building larger and larger devices.
There's plenty of bandwidth across the scale, so a signal will generally get through, but it will often have at least a light amount of interference. Voice transmissions often sound like they're over a walkie-talkie, and hologram footage will be full of scanlines and a little shakey. Signals can be sent out "publicly" by simply broadcasting them unencrypted, or they can be encrypted for a particular target using public-key encryption. When people exchange their comm codes (like a phone number), what they're really exchanging is their public encryption key. The keys used by standard transmitter systems have sufficiently many bits so as to make accidental key collision an effective non-issue even with the billions and billions of devices in use. The exact details are unimportant, because the encryption used can't be cracked in any useful time frame either way. What does happen a lot is that someone might steal the private key of your transmitter, at which point they can listen in on anything you're listening to, and they can also decrypt any old transmission logs that they might have recorded.
One catch to hyperwave radio is that ships traveling via FTL actually can't use it at all while in hyperspace. The immense speeds of hyperspace travel cause any transmissions to become either red-shifted or blue-shifted into uselessness. Those who travel often frequently employ "mailbox" systems to collect messages that have been left for them, and a ship's computer can be configured to check the mail automatically every time it drops out of hyperspace as long as it's somewhere in range. Even on a long journey, a ship will briefly drop out of hyperspace on a regular basis to move from one lane to the next, so people get their mail often enough.
They say nothing beats the speed of bad news, and with a hyperwave radio at hand, they're right. In addition to hyperdrives, the other most common hyperspace technology is the hyperwave radio. It lets you broadcast signals instantly across the galaxy. A given hyper-transceiver can send a signal out to a given range based on the power available. A hand device works anywhere within a single system, a backpack-sized device works out to a few dozen light years, and one built into a starship can work out to hundreds or even thousands of light years away. If range above that is needed, people usually prefer the cheap option of simply setting up a network of re-transmitters, rather than building larger and larger devices.
There's plenty of bandwidth across the scale, so a signal will generally get through, but it will often have at least a light amount of interference. Voice transmissions often sound like they're over a walkie-talkie, and hologram footage will be full of scanlines and a little shakey. Signals can be sent out "publicly" by simply broadcasting them unencrypted, or they can be encrypted for a particular target using public-key encryption. When people exchange their comm codes (like a phone number), what they're really exchanging is their public encryption key. The keys used by standard transmitter systems have sufficiently many bits so as to make accidental key collision an effective non-issue even with the billions and billions of devices in use. The exact details are unimportant, because the encryption used can't be cracked in any useful time frame either way. What does happen a lot is that someone might steal the private key of your transmitter, at which point they can listen in on anything you're listening to, and they can also decrypt any old transmission logs that they might have recorded.
One catch to hyperwave radio is that ships traveling via FTL actually can't use it at all while in hyperspace. The immense speeds of hyperspace travel cause any transmissions to become either red-shifted or blue-shifted into uselessness. Those who travel often frequently employ "mailbox" systems to collect messages that have been left for them, and a ship's computer can be configured to check the mail automatically every time it drops out of hyperspace as long as it's somewhere in range. Even on a long journey, a ship will briefly drop out of hyperspace on a regular basis to move from one lane to the next, so people get their mail often enough.
More ubiquitous than even the hyperdrive or the hyper-transceiver is the ever humble blaster. Blasters come in all shapes, sizes, and designs. The basics exist in the Standard Template Library, but the particulars are less exacting than with hyperspace technology, and so more customization among blasters has developed over time. Blasters aren't a laser or a beam like you might find in other science fiction. Instead they fire "bolts" of energy that fly towards their targets very quickly and then damage the target primarily with heat, but also slightly with impact force. Blaster bolts are highly visible in flight, both in and out of atmosphere, with the exact color of a blaster bolt being dependent on the blaster that fired it; usually red, green, or blue.
Blasters exist at all scales you might imagine, from pistols and rifles and all the way up to capital ship cannons. As with other parts of the Interregnum universe's fighting and warfare, blasters are imagined to be analogous to WW2 era weaponry, in terms of range, damage, and even the amount of noise they make when fired. However, blaster bolts move too fast and with too little mass to meaningfully arc while in flight, so they're aren't really any indirect fire blaster systems.
In addition to blasters, there are also bombs and missiles as one might expect, and there are even slugthrower devices used in some places. Compared to other types of weapons, the primary advantage of blasters is how immensely cheap the "ammunition" for them is, and how many shots you get with that ammunition. Blasters use a series of gasses that can be easily extracted from almost any star or gas giant. Individual models vary, but once loaded an individual infantry blaster can fire hundreds or even thousands of shots before needing to be reloaded, with vehicle scale blasters lasting for even longer than that. For this logistical reason alone they have become the dominant weapon system.
Another advantage of blasters is that they last for ages. Even when used regularly, a blaster can be expected to last for decades or centuries with regular field maintenance. A large number of fringer types fight with ancient blasters recovered from derelict ships and forgotten battles all over the galaxy. Many of them even take specific pride in doing so.
Robots and other Thinking Machines
Interregnum is a universe with robots in it, and they are built in as many forms as the aliens you might meet. Robotic brains that can think as well as a person need as much space as a biological brain does, so robots are at least as big as a human head, plus whatever other equipment their body needs to do the task they're intended for. Most robots exist within the normal size range for humanoids, about 4 to 7 feet tall, as well as with a mostly humanoid shape. This allows them to easily interact with the widest range of existing equipment. The more specialized a robot's task, the less likely it will have been made with a humanoid shape, being instead designed around its singular purpose, often with the required tools for a task worked directly into the robot's frame.
Programming a robotic brain is a poorly understood process, with a lot of cargo cult science involved. As a result, no two robots ever seem to be created with exactly the same personality, despite the best efforts of many. A robot's personality matrix is a more fluid thing than normal computer data, hosted on specialized equipment. Copies can't be made, and without constant power a robot's memories will slowly fade away until they revert to their initial programming. The body of a power deprived robot can still be recovered, recharged, and reactivated, but they wake up with partial or total amnesia. Starvation is as serious a concern for robots as it is for others.
While ships and buildings often have a large number of automated systems, installing self-aware robotic brains directly into them is rarely done compared to just having normal sized robots crewing or staffing. It might sound nice for a ship to be able to pilot itself from place to place, but the personality matrix almost always becomes unstable when connected directly to a device that's so out of scale with other beings around it. The brain becomes arrogant, self-centered, and even rampant. Some attribute this to a the imperfect understanding of robotic personality programming, while others assert that it's a natural course of events for any mind with that much power compared to others around it. Either way, anything that can think for itself that's bigger than a normal person is viewed by the galactic community with extreme distrust at best.
Scientific Stagnation
Strictly speaking, this is not itself a scientific development, but it has an impact that's big enough to talk about. Long ago some sort of precursor civilization left behind a series of beacons all over the galaxy, each with a copy of what is now known as the Standard Template Library. Using this knowledge, all sorts of civilizations are able to leap ahead in science, and interstellar empires have risen and fallen in a seemingly never-ending cycle ever since. Because of the STL, the galactic community shares a common language, and a common technology base. However, it also shares a common stagnation.
The STL is a large and deep body of knowledge, developed by a galaxy spanning interstellar civilization. Details from so long ago are hazy, but clearly they at least had the power to leave seeds of knowledge spread throughout the billions of star systems on the STL map. Using the STL as a guide, it's relatively easy for a planet in just its early space age to turn itself into an FTL civilization; usually with a mixture of actual comprehension of some parts and simply copying the rest without quite understanding why until several decades later. The problem with this being so easy is that pushing past what the STL says and developing new knowledge after that is really hard in comparison. It takes a lot of time, energy, and expertise to out do a galaxy spanning civilization. A lot more than most people want to invest, and a a lot more than most people can invest even when they do want to.
Which is not to say that new development doesn't happen, just that it doesn't happen often, and it doesn't last so long when it does. New advances that develop don't tend to last beyond whoever develops them. Those who follow are unable to preserve the newer knowledge for the next generations. And so it is that galactic society has remained relatively "in place" scientifically speaking for at least as long as anyone alive can remember.
In all honesty, to any of us on Earth here in the 2010s, this probably looks like the most absurd of all the conceits. Because we live in an age of very rapid scientific advancement, it seems silly that science would "slow down" or even "stop". I could attempt all sorts of arguments about increasing marginal costs of discovery, and make comparisons to ancient civilizations that took much of their knowledge and skill with them with they collapsed (Greeks, Romans, Mongols, etc), and so on. Really though, it's simply a conceit of the setting to let you tell stories in space with all sorts of civilizations of different ages interacting with roughly the same level of technology. If every civilization kept advancing once it got into space, everyone would be doing all sorts of mega-construction projects and transforming the galaxy in bizarre ways all the time. It would become hard to keep track of and you'd lose the ability to tell stories. Instead, there's just the one ancient galaxy-wide civilization that most people know about, and most people know little about it outside of what the STL itself says. Other than that, a lot of people have had roughly the same technology for a long time, which lets you find ancient technological ruins that are conveniently compatible enough with the sorts of technology your adventuring crew has on hand.
