Worlds of Design: How "Precise" Should RPG Rules Be?

I was watching a game played with a dice pool, and could see that the GM was waiting for the dice roll and then deciding by what felt right, rather than having any kind of precise resolution. How precise are the RPG rules themselves, and what are the consequences of imprecision?

But, he thought, I keep them with precision. Only I have no luck anymore. But who knows? Maybe today. Every day is a new day. It is better to be lucky. But I would rather be exact. Then when luck comes you are ready.Ernest Hemingway, The Old Man and the Sea

In answering this question, I thought about FATE and its fudgable (by design) rules. It moves far toward storytelling aid and away from traditional game. Contrast the relatively short FATE rules with the vast rules of versions of D&D beginning with Advanced D&D (1e).
[h=3]Miniatures-Based[/h] From a board gamer’s point of view, much about miniatures rules is open to negotiation, a reason why there are referees at so many miniatures battles. Fantasy RPGs derive from the Chainmail miniatures battle rules, not from board games.

Board games must have precise rules. There’s no GM (in almost every case) to interpret or to be rules arbiter. RPGs can get away with vague or incomplete rules because there is a GM (in most cases). On the other hand, an RPG is trying to cover “everything” that might happen, so naturally the rules tend to be much longer than the rules for a board game.

Precision in rules is important to a game’s GM philosophy. If the GM is merely a rules arbiter, then precise rules are vital. If the GM is a god-like guide who is above the rules, less precise rules work. It’s easier for a GM to be a rules arbiter, and that expands the potential pool of referees. We saw this especially clearly in 4e D&D.

Video games must have precision underneath, for programming purposes. Video game design documents (or whatever system is used) must be explicit and complete, so that programmers and other game developers can do what the designer intends.

It’s very difficult to be both precise and concise. When I’ve playtested a board game solo several times, the rules I then write will mostly cover the basics. By the time I’m done with the game (likely years later) there have been questions that required additional explanation, and even though my philosophy is to simplify a game rather than add things to it to solve problems, the final rules will be half again as long as the early ones in order to provide clarity and precision.

"Legalese" is an example of rules-writing gone way too far to the side of precision. But one person’s legalese is another person’s precision.
[h=3]“Reasonable” Players?[/h] The writer of the following comment epitomizes the “rules don’t require precision” attitude:

"[Game] Writers tend to be too wordy and explain everything in excessive detail when in fact their readers are perfectly capable of drawing their own conclusions from just a bit of input." --anonymousmagic

This advice may work for RPGs, where you have both a rules arbiter/god and a group of players who can restrain the rules lawyers in the group. If you're designing a game where people won't be very competitive (no "rules lawyers") then this can work. But it’s bad advice if you're designing a competitive game.

I like rules that are similar to technical writing (instructions), that attempt to be exact rather than "reasonable". Because there are *lots* of unreasonable game players, especially for two-player games where there might not be a majority of reasonable players to rein in the unreasonable one.
[h=3]Chrome[/h] “Chrome” is exceptions or additions to the basic rules to provide much of the color and flavor of historical games and fictional games. But as exceptions/additions to the basic rules it adds to the length and complexity of the rules.

Take the simple example of leaders in a wargame. Standard Risk has just a single kind of unit, the Army. There are no leaders. In Britannia there are a number of leaders, even though most armies are of one basic type, with the leaders adding to the dice roll in combat. Simple enough, but leaders provide a human element in a game about a thousand years of history. In Diplomacy, a faceless World War I game, an epitome of simple that relies on player-to-player negotiations for most of its interest, there are no leaders.

In RPGs, which are the opposite of facelessness, almost every designer will want lots of “chrome” to help represent a “real world” experience, even if it’s a fictional world.

How precise should RPG rules be? “It depends.”

This article was contributed by Lewis Pulsipher (lewpuls) as part of EN World's Columnist (ENWC) program. Lew was Contributing Editor to Dragon, White Dwarf, and Space Gamer magazines and contributed monsters to TSR's original Fiend Folio, including the Elemental Princes of Evil, denzelian, and poltergeist. You can follow Lew on his web site and his Udemy course landing page. If you enjoy the daily news and articles from EN World, please consider contributing to our Patreon!

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Lewis Pulsipher

Lewis Pulsipher

Dragon, White Dwarf, Fiend Folio


That one‘s nasty.

If that happens too often, you need to switch the design approach from some lofty high goal (fits on one-page, unified mechanics, beautiful bell curve to imagining a certain play experience and then writing towards that until the mechanics fall into place (no matter how dirty the math or quirky the rules).

Anyway that‘s what playtesting is for.
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Seeing as this thread has been necro'ed and I seemed to miss it first time around:

Here is Vincent Baker on the purpose of RPG rules:

Roleplaying is negotiated imagination. In order for any thing to be true in game, all the participants in the game (players and GMs, if you've even got such things) have to understand and assent to it. When you're roleplaying, what you're doing is a) suggesting things that might be true in the game and then b) negotiating with the other participants to determine whether they're actually true or not. . . .​
So look, you! Mechanics might model the stuff of the game world, that's another topic, but they don't exist to do so. They exist to ease and constrain real-world social negotiation between the players at the table. That's their sole and crucial function.​

That suggests that mechanics need to be precise enough that we can tell when they are to be used - ie when does free roleplaying stop and the rules come into play? - and we can rely upon them to resolve the matter that led to them being invoked. What counts as resolving the matter will vary depending on what bit of the real-world social negotiation we were hoping to ease or constrain. The most common, I think, and speaking in general terms, is determining who gets to say what happens next. Because that in itself might trigger a new need for rules, I think there will be some overlap between precision of rules activation and precision of rules outcome.

Here's another post by Vincent Baker, on different sorts of rules and how they relate to character creation:

I say, "my character, this guy in Thatcher's london, who has everything to lose, he goes to his lover's flat and convinces him to keep their affair private." You say, "y'know, I don't think that his lover is inclined to keep their affair private, do you?" And I say, "no, I suppose not, but my character is desperate to convince him anyway. In fact, he brings an antique revolver with him in his jacket pocket, in case he can't." . . .​
How do we decide what comes true?​
We can simply agree. That works great, as long as we really do just simply agree.​
We could flip a coin for it. Let's do that: heads my character convinces yours to keep their secret, tails he murders him instead.​
Or y'know, that's a lot to deal with. Let's have a rule: whenever a character's life is at stake, that character's player gets to call for one re-flip of the coin.​
On the other hand, isn't my character's life at stake too? His wife, his kids, his position, his money, his everything? Which should have more weight between us, your character's life or my character's "life"? Shall we go best two of three, or is that setting life and "life" too equal?​
How about this: we'll roll a die. If it comes up 1 or 2, your character will refuse and mine will kill him; if it comes up 3-6, your character will agree to keep the secret and (unknowingly) thereby save his life. It's unequal because my character killing yours is less to your liking than your character ruining mine's life is to mine. It's unequal to be fair to us, the players.​
Notice that we haven't considered which is more likely at all. We probably agree that it's more likely, in fact, that your character will refuse, so my character will shoot him. But that doesn't matter - either could happen, so we roll according to what's at stake.​
Also, notice that we aren't rolling to see whether your character values his life in the face of my character's gun in any way. We're rolling to see if your character agrees to keep the secret without ever knowing about the gun, or if he refuses without knowing about the gun and my character shoots and kills him. . . .​
Let's add another wrinkle. Let's say that at the beginning of the game, we each choose a sure thing, a limited circumstance where we don't roll, but instead one or the other of us just chooses what happens. I choose "my character's children are in the scene." You choose "once per session, at my whim."​
Here, this late, I've finally made a mechanical reference to the fiction of the game. I still haven't considered probabilities at all, and do you see how "my character's children are in the scene" and "once per session" are the same? They're resources for us to use, us the players, to have more control over what becomes true. . . .​
But so okay, that's pretty good, but how do we come to agreement about the two possible outcomes in the first place? Here's a rule: neither outcome can overreach the present capabilities of the characters involved. That makes sense; if my character didn't bring the revolver, I shouldn't be insisting upon "shoot and kill" as a possible outcome, right? Same with my character's skills and foibles as with his belongings. Like, if I establish that my character has a weak heart, that opens up some possible outcomes for us to propose; if I establish that my character is an excellent driver, that opens and closes some others.​
Come to think of it, when do I get to decide if my character has access to an antique revolver, has a weak heart, is an excellent driver? Do I get to decide on the fly or do I have to declare it up front?​
Either way, I should write all this stuff down on my player sheet, as I establish it. That way I know what I'm allowed to propose as possible outcomes.​
See how this goes? The "character sheet" isn't about the character. Maybe - maybe - it refers to details of the character, if that's what our resolution rules care about. But either way, even if so, the "character sheet" is really a record of the player's resources. "Character creation" similarly isn't how you create a character, but rather how you the player establish your resources to start.​

Is when my character's children in the scene precise enough? What about a modern game, where the children might be physically distant but on the phone? Is I get to decide what happens next - the rules outcome, in Baker's imagined game, of my character's children being in the scene - sufficiently precise? In a mechanically light, fiction-first game the answer will probably be yes. In a game with a complex action-economy structure, probably not. In a game which has tight constraints (be they implicit or explicit) around who can be in a scene, maybe yes. In a game which permits scenes with many characters in them, maybe no - if my character is leading a warband in an attack, and my children are with me Lone Wolf and Cub-style, do I just get to decide that my warband wins the skirmish?

So without knowing how you want the play of a game to unfold, in terms of the nature and scope of the fiction and the nature and scope of the participants' roles, it's hard to say anything very precise about how precise the rules should be!


Should implies ought and in that sense there is no right answer. Play the games that suit you and your group.

Now having said that, and reading between the lines, I will answer how I would like the rules to be for my games.

1. I like simple mechanics like d20 roll high against a DC. I'm okay if there are two or three options just not twenty five. So having a special table for everything is probably bad if it is used during play time. It's fine as a GM aid during prep time when there is not pressure to give an answer.

2. I'd like to have some guidance and examples on how things should be adjudicated. I'm fine with the GM making judgment calls beyond that point for a very specific situation. If the situation though comes up a lot then I think there probably should have been an example in the rules.

3. I want a game designed to let the dice fall where they will. So if the GM is fudging all the time that is a failure of the game system. In fact personally, I never want to fudge when the die roll matters.

4. I like a good amount of what I call details. So I want a spell list and not just make up something and roll for it. I want players to feel confident they know what they can do with what they have most of the time. Same for skills, feats, whatever.

So 3e/PF may be a bit too crunchy for me. Fate is probably not enough. I'm an OSR guy. I'm specifically liking ACKS right now. C&C is another solid option. I want modern game design but I want somewhat streamlined mechanics.

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