Anatomy of an RPG

This is the first issue of my column on RPG mechanics and RPG theory. Never in here will specific RPGs be discussed at length; this is a column about RPG mechanics as a whole. This month’s issue, not unfittingly, is a detailed anatomy of RPG mechanics themselves. This should prove useful to RPG designers by allowing them to split their mechanics up into bits. Things are always easier to do if you can split them up. It also drops some nice hints on mechanics…
All rules in RPGs can be divided into two categories; character description and action resolution. You need rules in each for the RPG to be playable. The cleaner the mechanics, the more separate they are. In D&D, for instance, the character description are hoplessly entangled so it’s hard to distinguish one from the other, wheras in GURPS, you can clearly divide character description and action resolution. The ideal RPG would have these two sections capable of operating independently. In the rest of the article, I will split these two categories into more categories and detail on each.

Character Description

Character description invloves describing characters using various descriptors (skills, for instance), and assigning values to them, usually numbers. A quick list of ways in which a descriptor can be described:

  • Quantative- a number. A quantity.
    • An integer.
    • A percentile value.
    • A range. Such as 1d8 (1-8). More on random number generators later.
  • Qualitative- anything that it not measurable as a quantity. A quality.
    • A concrete value, such as “female”.
    • An abstract value, such as “unlucky”.
    • A general value, such as “elf”.
    • An adjective, such as “strong” and “very strong”.

Now some discussion of distribution of these descriptors. RPGs tend to divide descriptors into attributes and skills (though most use different terminology). Attributes are descriptors which describe the character’s raw abilities, while skills are their training and experience. There are actually several generic categories:

  • Attributes- quantative descriptors representing raw abilities.
  • Skills- quantative descriptors representing training and experience.
  • Advantages, Disadvantages, and Quirks- qualitative descriptors representing almost anything.
  • It seems worth noting that D&D has categories for attribute-type quantative descriptors, attribute-type qualitative descriptors, skill-type quantative descriptors, skill-type qualitative descriptors, various assumed descriptors (see below), plus assorted odds and ends (such as Size), plus whatever the magic system is. This is a stark example of mediocre game design. RULE OF THUMB: If a game system needs a separate system for magic, you should probobaly ditch it.

Now some assorted descriptor anomalies and peculiarities:
Assumed Descriptors: Almost all RPGs do not list many descriptors, but simply “assume” them. Take D&D for instance:
Assumed Descriptors in D&D

  • Height, weight, others such as hair and eye color
  • Gender
  • Alignment (!)
  • Religion

It is my humble opinion that you should never, ever use these, because you can’t assume anything. According to this, dragon characters have hair colors, and worse, centipedes have religion. And that’s without even stepping out of the fantasy genre! These may be okay in genre-specific RPGs if carefully thought out, but never, ever in universal RPGs.
Adjectives as opposed to numbers: Many RPGs (such as FUDGE and The Mirror, couldn’t find a link, sorry), choose to use adjectives instead of numbers for their quantative values, on the grounds that they tell you more about the character. What these RPGs fail to do is work the adjectives into the game system seamlessly. They essentially use the adjectives as a subsititute for numbers, and in the case of The Mirror, as a thinly disguised range pretending to be an adjective. I have yet to see a system using well-designed adjective-based quantative values.

Action Resolution

Action resolution involves weighing various descriptors of PCs, NPCs, and outside forces to arrive at a conclusion which determines logically the outcome of a certain situation.
Data Processing: Action resolution is all about processing data. You get data from character description and then you do things with it with action resolution. A successful action resolution is one that provides realistic results and covers as many situations as possible with as much speed as possible. The features you look for in an action resolution system look eerily similar to those you look for in a computer:

  • Processing a wide variety of data.
  • Producing high-quality results.
  • Processing data quickly.

At this point, I will burden you with one of the design epiphanies I have had in recent months: You can gain a lot by thinking outside of the box. You can probobaly gain more by stepping out of the box and finding what is already there. For instance, talk to a programmer about RPG design and you will probobaly get some good insight on RPG design drawing ideas from, say, Object Oriented Programming. Talk to a philosopher about RPG design, you will get concepts drawn from philosophy. This advice may be less useful, though, because philosophy is rarely as concrete as programming. Therefore, I conclude that one can draw an infinite amount of inspiration for RPG mechanics by looking at existing logisitical schemes. Let’s take an example; our timekeeping system.
Timekeeping is about measuring numbers; therefore, we will be using the logic scheme used to divide up time to divide up quantative values. Instead of measuring values on one scale, we divide them up into seconds, minutes, hours, days, weeks, etc. This means we can now have a value of 6 be a value of 1 with a higher unit. Incidentially, this system is highly impractical, so we adapt it. We use base 1 units. Now we can shave some zeroes off of round numbers by using higher units. This is a nice rules fragment, if we can work it into the system; working-in is the main difficulty of adapting existing logic schemes.
Okay, that huge tangent complete, back to action resolution.
Randomization: Almost all RPGs have some way of introducing random factors to action resolution, usually using dice (and with good reason; dice are one of the more practical and powerful random number generators out there). Most systems that advertise themselves as diceless use cards or some less convenient random number generator. This silliness falls into the same category of using adjectives instead of numbers; unless you can make it work, don’t do it! Anyway, back to random numbers. There is an incredible amount of detail that I could go into on this (see John Kim’s dice mechanics article for said detail), but I won’t. For now I will just cite a few things I find interesting:

  • Ranges: Like those things in The Mirror where you have just a die roll for each of your descriptors. This is a very good method of randomization (aside from the cost of dice) if you can make it work, which is easier to pull off then the other schemes I have said that about. The nice thing about this is that if randomization uses any random number generation, everything is a range. So, if you can come up with a practical way to initiate the generation of any range in one step, all action resolution will be one-step. The trick is finding a number generator that can do this pratically.
  • Varying Degrees of Randomness: Some RPGs put more weight on the random number generators than others. In some RPGsD&D, this can vary based on the situation, which is more a result of poor design than intent. However, there is something very good in here. While there is clearly no determinable answer to how random your game should be, there are three answers, one of them inspired by the silliness of D&D:
    • Variable Randomness: The randomness varies logically by situation, much like D&D, except D&D varies randomly like an electrified hula dancer. What we want is an RPG where the degree of randomness is based on the degree is randomness that is logical. Someone let me know if you figure this one out.
    • Customizable Randomess: The GM can determine how random they want their game. This is a tough one, but I pulled off a similar thing in my RPG by letting the GM vary how precise they wanted to measure player abilities.
    • A Combination of Both: If the GM can vary the randomness on a case-by-case basis, then they can fit not only their preference, but realism also. This may be the best solution, and also the hardest to make workable. It does present all sorts of opportunities for imbalance. Suggestion: Character stats are based on a die and a number added to it, such as 1d4+6. Well, if the GM could vary this by taking 1 away from the number to be added and adding 2 to the sides of the die, then he could vary how much of it was random. For instance, 1d4+6 could become 1d6+5 if he wanted more randomness, or 1d2+7 if he wanted less randomness. This is impractical on several levels, but just an attempt to prove that you can come up with mechanics to accomplish this stuff.

Now, a graphic:

It turns out that this graphic is not only as cute as a button, but describes the layout for the rules scheme of almost any RPG. I used a few new terms here, so let’s take a look at them:

  • Generic Descriptors: Descriptors which apply to all characters, or at least most. Like ability scores in D&D.
  • Specific Descriptors: Descriptors which make a character unique, or at least less generic. Like skills in D&D (and feats, and class, and spells, and..)
  • Data Acquisition: Before it can process data, the action resolution system needs to get some data. What data does it use? Is it quantative or qualitative? What kind of quantative or qualitative?
  • Data Acquisition: Before it can process data, the action resolution system needs to get some data. What data does it use? Is it quantative or qualitative? What kind of quantative or qualitative?
  • Variables: The information about the outside world that the resolution system acquires. While descriptors are predefined, this is more interesting because you need to figure out how you want to describe the variables. It is generally a good idea to make it as similar as possible to the way the descriptors work, for easy compatability.
  • Factor Weighing: You need to figure out how the data acquired will interact. For instance, most systems use “the highest number wins” (and there is nothing wrong with this). Straightforward and modeled after reality are good traits to go for.
  • Random Number Generation: To add that element of uncertainty. The value of random number generation is debatable, but you should all of the aforementioned factors if you intend on using it.

In conclusion, there are an obscene amount of ways in which you can design your RPG, and no shortcuts, but working on one piece at a time and keeping your goals in mind while doing so will probobaly end you up with a good RPG. Also, study up on RPG mechanics. The better you understand how RPGs work, the more easily you will be able to build them.

This article by Nick, who thinks he may have made an RPG for everyone: Don’t be afraid to tell him if he’s wrong. You can contact him at


2 Responses to “Anatomy of an RPG”

  1. Paul Babin Says:

    Thanx ,
    This was very helpful … I am in the process of creating one . I’ve only played 1 game for a short period of time ; wich wasn’t made very well but I seen potential . Most people have sayed that A person should have played alot of these games before attempting to create his
    own . I think this statement is very true on many levels …however I feel that on one level ,I have the upper hand wich is the indoctrination of r.p.g . traditions . Some people are led to believe that on in certain aspects of gameplay there is “only” the tried and true -method . I am hoping that during this creation ; I will be able to go from the making of the wheel to the discovery of fire.

    So thanx for your essay this is the kindling to start this fire

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