24XX devlog: The SRD

The 24XX System Reference Document (available on Itch.io and DriveThruRPG) is a free, Creative Commons licensed version of the rules used by the 2400 lo-fi sci-fi RPG series (also on Itch.io and DriveThruRPG).

I was on the fence about writing about the SRD in a series of 2400 devlogs because the 24XX SRD is not, strictly speaking, a 2400 game. But I keep hearing positive feedback from people about this blog series, and the SRD is (to me) an important outgrowth of 2400.

This post is not explicitly about how to hack 2400 and the 24XX SRD for your own games; I’m spreading that out over a number of other posts, including these devlogs, with (loose) plans to compile it all later (somehow). Rather, this post is more about why the SRD is what it is (and isn’t what it isn’t), and how I might have done things differently if I knew when I made it what I know now.


I don’t remember what John Harness said to inspire me to put as much as I did into SRD, but he deserves credit for making it happen as co-host of the 24XX Jam. It may sound funny to phrase it that way — “as much as I did,” like it’s a whole ton of stuff, when the document part of the “system reference document” is only three pages and a cover — but it actually took a decent amount of work. I tried to pack a whole bunch of useful stuff in there.

I’ve seen a few different angles of approach to making hackable rule sets, but the one that most impressed me in its format was Ben Milton’s Knave. It’s not just a rules document, but a sample layout, design notes to advise you how to work with it, some actual content you can use at the table (and in your own hack!), and a template you could copy from and alter directly in a file format more common that Adobe InDesign documents.

Just as you don’t have to make a Knave hack that looks just like Knave, don’t have to make 24XX games in the exact same format as my template. Go longer if you want! Mix up page size and layout! But for folks who do want the path of least resistance, I wanted to make it easy to just alter the text and throw in a new cover image. I know that going in with some constraints, and sticking with a short format, makes it a lot more likely I’ll finish a game — it makes it feel more approachable, more finishable — and I figured I wasn’t alone in that.

I didn’t entirely follow Knave’s example. I opted not to use Microsoft Word files because I personally found it a huge pain to modify the Knave document for Grave. And I actually like having cover art: It gets me excited to work on a game, gives me an excuse to practice graphic design, inspires readers by setting the tone more quickly than text alone can do, and ultimately helps sell the game. So, I made versions for Affinity Publisher (the software I use myself, which is more affordable than paying a monthly fee for Adobe Creative Suite), Google Docs, and Google Slides — with tips for getting cover art into them — plus a plain text version. (The InDesign document came later, thanks to James Lennox-Gordon, creator of the 24XX fantasy series, 1400.)

Just a heads up, in case you plan on releasing your own SRD: Maintaining it in four different formats yourself is a lot of work! I sometimes get folks asking me if I’d like to update the HTML versions they put up online, but I can’t. Anybody can create an online version thanks to the Creative Commons license; I can’t commit the time to update them all when I’ve got so many documents of my own to keep in sync.

In addition to the work of creating the SRD itself, it took some time to put together supplemental options and tips. I use commercial typefaces for 2400, but I found some good free equivalents for designers who want to emulate the style. I also tried to give some tips and instructions for drawing from the same well of art that I used (and then later had to add caveats, after realizing it was not all Creative Commons licensed, like I had been mistakenly informed it was).

As much as I appreciate the brevity of the SRD, I could also see the value in expanding it to fit the expanded rules text from Emergency Rules or Battle Moon. I know I could save myself some work by just making those Creative Commons licensed too, but I’d really rather keep 24XX its own thing — the thing I’m clearly giving away — and not confuse that with the game I want to be mine.


I released the 24XX SRD under a Creative Commons Attribution 4.0 International license (CC BY 4.0). This has worked fine for my purposes, but if I were to do it again, I’d probably do it as a custom license more like Mark of the Odd or the Mörk Borg License.

I had been hesitant for a long time to release a game under a Creative Commons license. For one thing, I saw what Stuart Robertson went through when his CC-licensed OSR logo got co-opted by bigoted jerks. He tried to assert that those people couldn’t use the logo according to a “no bigots” assertion of the license. I threw something like that into my own SRD just in case), but I suspect it’s not realistically enforceable. And in Stuart’s case, it didn’t really solve the situation for him; it was still a stressful enough experience to appear to drive him off the face of the internet awhile.

In addition, I had an uncomfortable experience putting a CC license on one of my own games. Another designer copied a decent portion of my game, pasting it into their game unchanged. The document did name me as an “inspiration” … alongside about a dozen other, more widely known designers, with no indication of which parts came directly from my game. They released their game under a CC BY license, too — and suddenly it dawned on me anybody could grab a substantial portion of my game from that game, and start selling my content in a new package that doesn’t credit me.

Creative Commons licensing does not handle “lineage” very well. That is, all it requires is that you give a nod to to the last person you borrowed from, not the people they borrowed from. (At least last I checked.) This is wonderfully efficient if you want to encourage people to create freely! But as much as it embarrasses me to admit it, this bothers me a lot more than I expected. I’m not creating games to get rich or famous, but I’d be lying to myself if I said I didn’t care about getting credit for things I put a lot of work into.

And so, when I released 2400, I decided to keep it copyrighted by default — but I partitioned off the 24XX SRD in my mind so I could give that away, mentally prepare myself better to think of it as a resource that doesn’t just belong to me. It helps, I think, that I built it specifically to be used as a game-making resource, not just a game in itself. I want 2400 to be read and played and hacked, but I want 24XX to be torn apart and turned into things that belong to other people, maybe even things that make them money. Thinking of it this way makes it easier to feel happy to see people using that material, knowing I gave it away for that specific purpose.

And it does make me happy. But I think I still prefer custom licenses like the ones I linked above.

The main advantages to using a Creative Commons license, as far as I can tell, are that they’re legally enforceable and widely recognized. But let’s be honest: Most indie publishers can’t afford to enforce a breach of license no matter how carefully it’s crafted, and CC licenses are not nearly as widely understood as CC advocates seem to think. I often see people goofing up attribution and usage of my own SRD, and the thing’s only three pages long, with explicit instructions in the SRD itself. You don’t even have to go to the Creative Commons website to find out what to do!

More people don’t goof up than do — but still, I can’t help but wonder if having a standardized license that people think they know discourages some folks from actually reading the terms of the license. In the case of a custom license, you have to read it to know the terms … in theory.

Defining “24XX”

One thing that is nice about a Creative Commons license is that I can wash my hands of the responsibility defining what “counts” as a 24XX game. “24XX” now belongs to the world! I take the PbtA approach: Slap it on your game, follow the terms of the license, and I won’t say you’re wrong. But what the heck, in case you really feel like you need reassurance, your 24XX game…

  • Can be any length you want
  • Can use other dice ranges, other dice, or no dice at all
  • Can bolt on rules from other games (yes, even hit points)
  • Can have modifiers added to rolls (even though I won’t play it)
  • Can be GMless, or solo, or whatever
  • Doesn’t need to have “24XX” on the cover

Someday I’ll tell you what I think defines 2400’s rules, at least. But I put the 24XX SRD on its own page, and not as part of the 2400 bundle, because I want it to be its own thing, not just my thing. I want you to feel free to deviate from 2400. I want you to make your game. I just hope I can make it a little easier for you to make your game.

When Spencer of Gila RPGs asked people what game they’re proudest of for a list of “Proudest Games,” I didn’t say 2400, my highest earner — I said this, the free 24XX SRD. And that’s not because I’m so proud of the rules, which are mostly designed to be intentionally easy to replace or ignore. I’m proud because it has been hacked by a range of different designers over 100 times, and counting — which means it’s doing exactly what I meant it to do. It’s helping people make games.

Please don’t let anybody tell you that your game isn’t a 24XX game because it doesn’t fit their idea of what 24XX is. At the end of the day, I just want you to make your game.

Featured image edited from original CC BY Beeple (Mike Winkelmann)

3 responses to “24XX devlog: The SRD”

  1. I just wanted to leave a quick thank you for creating such a well-conceived and executed SRD. You’re right to be proud of it!

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