There’s an idea I think about a lot when it comes to RPGs – “How does THIS particular game teach you to take the in-game events and turn them into mechanics? How does it teach you to take the mechanics and make events in play?” (see also: Vincent’s “How RPG Rules Work” or Quinn Murphy’s “Thingification” idea)

When a game makes this easy to understand and smooth for the group playing, it’s really easy to take anything that happens in play, and figure out how it fits with the mechanics, or to take anything the mechanics kick out and make it an event in the imaginary events. (As I tend to say, the easiest rule is “I say this happens, and then it does”). When this is complex, challenging, or just poorly explained, you end up having lots of problems for groups – you can see a lot of this around D&D 4E’s mechanics and the complaints with it.

Anyway, that translation process either differentiates the “things” in the game by fiction, or by mechanics and it’s important because these are two very different ways to do a game.

Differentiation by Fiction

So, let’s say we’ve got a game, and it’s got dragons: ice dragons and fire dragons.

Here’s one example:

Fire Dragons: 20 hitpoints, 1d6 fire damage per round

Ice Dragons: 20 hitpoints, 1d6 ice damage per round

So, in this example, the dragons are basically the same, and the only difference is we’ve swapped one word for another. The only thing that makes them different is fiction based – we can describe that ice attacks work different than fire attacks, but there’s nothing mechanically that necessarily makes them that much different.

This is differentiation by fiction.

You can see some games are built entirely on this idea – Primetime Adventures, Inspectres, HeroQuest, FATE games, Universalis, etc. The mechanics are universally identical, you just swap descriptor words to change one to another.

It’s really useful if you want a game where the mechanics are less deep in specifics, easier to get system fluency to make good choices in play, and it’s very easy to improvise or adapt – just swap some labels for another and there you go.

Differentiation by Mechanics

Now let’s try a different version:

Fire Dragons: 25 hitpoints, 1D6 fire damage a round, and target takes 2 more fire damage until doused

Ice Dragons: 20 hitpoints, 1D6 ice damage a round, and target is frozen in place for 2 rounds.

You can see here, that the dragon types work a little different and probably will require different ways to deal with in play. Specific mechanics result in specific differences, result in specific tactics.

This is differentiation by mechanics.

Most traditional rpgs use this – specific class/race powers, feats, a power tree, spells – things that give you access to mechanics or methods of play that you can’t get using the other options.

It’s really useful if you want a game where having deeper system familiarity is more important, where tactics or strategy might be useful, or if you want to push play choices in differing directions (“Doing X feels completely different than doing Y”).

What it means for play

The reason to look at this is that these are two very different ways to come at a game, and usually gets subsumed into some vague talk about “crunch”* (which has about 3-4 other factors piled into it as well).

With Differentiation by Fiction, you don’t have to think about mechanics much, but then the only thing you have to really push play, to make one thing behave functionally different than another is judgment calls at the table and agreement of the group (“Well, I’ve got Big Sword 4, but since we’re fighting underwater, it should have a penalty or not be useable at all.”).

With Differentiation by Mechanics, different choices matter much more, but it also means players need to develop some familiarity and fluency with the system to make that happen. It means a longer time spent learning the options, and trying to piece together why things work and what strategies work best. It also becomes a lot harder to improvise things if you find yourself having to suddenly come up with new rules or slam together systemic differences on short notice.

The way these two design philosophies operate is so different that players who prefer one type will not find systems that do the other worth touching at all. So this becomes important to know if you like only one type, if your group is a mix, or if you are designing a game.

(*One might think that fiction-differentiation automatically means “low crunch” but that’s not necessarily the case. Universalis, for example, has a good amount of procedural steps, and the latest version of HeroQuest also has quite a bit of crunch options that go along with it as well. Contrary, there’s also a few mechanical differentiation games that have relatively low crunch, such as basic D&D and many of it’s clone rpgs .)