Exception-based design?

[Archmage]

Forgive me if this is a dumb question.

Occasionally the issue of exception-based design and the problems inherent to it are approached for various reasons. However, likely because I've spent the majority of my gaming life inundated with WotC products like Magic and the d20 system, I'm not actually sure what the alternative is.

Can anyone shed some light on this issue or point me to examples of complex, evolving games that don't use exception-based design? Maybe, games that don't change over time can get away with this, but maybe I'm just misunderstanding--it seems to me like even Candy Land has exception-based design (draw a card and move to the next space of that color...unless, of course, you're on one of the "trap" squares).

[Blicero]

Every game is "exception-based," to some extent, but most people dislike 4E because it really hits the roof with making nearly every power "unique" in that it won't necessarily be anything like another power called the same thing.

(I think, in another thread Frank mentioned how in the basic MM, there's like three or four monsters that have a power called "Evil Eye," and they all do completely different things.

Whereas, in, say, 3E, things tended to be a bit more codified. If you use a knowledge check to identify a medusa and learn that it has a power called "petrify," you'll know that it'll probably work the same as the petrify power of a gorgon or whatever.

So 3E is really a bunch of little rules and exceptions to those rules, but the developers generally follow those exceptions and not just make up new rules every time they did something remotely new.

Does that essentially answer your question?

[TavishArtair]

Pretty much that. Earlier systems tended to be made out of function calls. They referred to other rules in the game extensively. In order to "simplify" itself, 4e decided that everything would be stated up front. There are still some function calls, but they are intended to be minimal. In reality, they removed the ability to standardize power design in exchange for this, since they no longer created a single code for how petrification resolved, for instance, and then referred to that, or for shapeshifting, and so on. It reduces pageflipping, sure, but absconds with rule consistency.

A better example of a blend of the two designs is in Magic, their Other Fine Game. Many spells are individualized powers like in 4e's D&D, but they also create standardized keywords for common things. Even 4e uses this keywording philosophy to an extent. However, by basing everything very strongly on the premise of "exception-based" design, without an analysis of what that actually means, they included perhaps less keywords than they should have.

In reality, all games will tend to have some combination of exceptions and function calls. The "pageflip factor" versus the "consistency factor" (the combination of which I have seen called the "chaos factor" once or twice) is ultimately what are being measured. If something has less pageflip but also less consistency, it is called exception-based design.

Never forget that the two are linked, also. You cannot simply standardize a set of rules for petrification, say, and then reprint those rules every time. You have to also keyword them, or else you cannot errata how petrification works without publishing individual errata to every single "petrification"-type power.

[Archmage]

That makes a lot of sense--it's not binary, there's a continuum of how "exception-based" something is.

So in Magic anything that has "flying" in its text box refers to a general rule regarding the treatment of flying creatures. Conversely, 4e has a few function calls to status effects (dazed, etc.) but for the most part doesn't actually obey any sort of consistency outside of some vague guidelines. Two powers that both have the Fear keyword might do completely different things since there's no single function call for fear effects aside from the hand-waving about how Fear keyword powers generally do X or Y but otherwise all operate differently.

[RandomCasualty2]

That makes a lot of sense--it's not binary, there's a continuum of how "exception-based" something is.

Yeah, it's generally more of a slider than anything else, which compares references to actual full mechanics. Basically if your character is just a series of named abilities and numbers, you're not using much exception based design. GURPS pretty mcuh shows you how this is done. Where you'll have a character with abilities like :

Innate Attack (3d toxic, area 3, lingering effect, noxious)

Now you have no idea how the fuck any of that works or what it means until you turn to the rulebook and look up what any of that shit is. Now chances are each of those abilities are on multiple pages.

A wholly exception-based design would be something like this ability.

Acid Breath: Requires a standard action to use, targets a 3x3 set of squares that must be adjacent to you. It deals 3d6 acid damage to all targets within the square. Each creature can roll a reflex save against a DC of 16 to avoid the effect. The effect lingers for 1d6 rounds, affecting each creature at the start of their turn. It also releases toxic gas that can nauseate a living target, making it unable to take any action except move actions. The nausea can be avoided by a fortitude save against DC 16. A nauseated creature remains that way until it leaves the nauseating effect and waits 1d4 rounds.

Now, as you can see, the exception based design version takes way more space, but also prevents you from having to flip pages.

However, having a less exception based design allows you to make better use of errata. If you for instance figure out that noxious is a broken ability or whatever, you can fix it in your main rules and also nerf everyone who took it at the same time. So monsters you released prior to the errata don't have to be updated individually. One change to noxious and you've automatically fixed every monster with that ability.

In fact, most of the time applying fixes to exception based games are a pain in the ass, so many, like M:tG just have a ban list of cards. They don't bother to try to make black lotus balanced, they just say "you can't use this."

Otherwise you end up with 4E's mountain of errata.

[virgil]

Why is only exception-based design the one that saves on page-flipping? Can't you have keyword/standardized abilities repeated on the individual entry if you're that concerned about page-flipping?

[TavishArtair]

Not only can you, but you often do in Magic: the Gathering nowadays. Obviously overly verbose abilities are left off of cards most of the time. However, 4e did not commit to this design, probably because it also did not want to have every single fear power work identically. Monster stats were designed much the same way. There are golems in the 4e PHB which are immune to the things you would think a golem might be immune to (poison, disease) and others which are perfectly vulnerable.

[RandomCasualty2]

Why is only exception-based design the one that saves on page-flipping? Can't you have keyword/standardized abilities repeated on the individual entry if you're that concerned about page-flipping?

Mainly because standardized systems tend to be more complex. This tends really to be the main draw of a standardized system in the first place, because it allows for a lot better ability interaction. The draw to an EBD system is that it allows for a lot of uniqueness. Every power can feel different.

This is really why I believe 4E failed. It was EBD, but it lacked any kind of unique feel. The classes just didn't play or feel differently. So unlike say, a game like Starcraft, where every unit has its own unique feel and unique special abilities, you ended up with a game where all the abilities just felt like trivial permutations of each other to the point you honestly didn't care which you used. In 4E, you never really got a sense of "this ability is mine, and it's what makes me special."

Mainly this was due to the fact that there were many classes but only a few roles and the roles performed very much alike. Every single fucking leader was a healer, strikers were for the most part just about inflicting extra damage, and every defender used the marking mechanic. Nobody really had a big specialty in 4E and rarely did anyone ever really shine. When battle broke out, you just did the same thing every time, which is was the thing your class is supposed to do.

[Murtak]

Magic is not an exception-based game.

Exceptions are deviations from the norm. When a rule says "do x, unless y, then do z" - that is an exception. Rules that say "do x, as if it were y" or "do x twice" are not exceptions. When you gain a DnD power that lets you deal double damage on attacks of opportunity that is not an exception.

If you want some nice examples of exception-based design look at 2E. IIRC the sleep spell specifically does not work on elves. That is bullshit - if you want to have a new creature who is also not affected by sleep you need to scour every spell and ability and rule that mentions elves for mention of sleep. Properly designed the sleep spell has a sleep or mind-affecting keyword or hands out the sleeping condition and elves are immune to that.

[The Man Who Killed Death]

Magic is not an exception-based game.

Exceptions are deviations from the norm. When a rule says "do x, unless y, then do z" - that is an exception. Rules that say "do x, as if it were y" or "do x twice" are not exceptions. When you gain a DnD power that lets you deal double damage on attacks of opportunity that is not an exception.

If you want some nice examples of exception-based design look at 2E. IIRC the sleep spell specifically does not work on elves. That is bullshit - if you want to have a new creature who is also not affected by sleep you need to scour every spell and ability and rule that mentions elves for mention of sleep. Properly designed the sleep spell has a sleep or mind-affecting keyword or hands out the sleeping condition and elves are immune to that.

It all depends on the norm. In your example about doing twice the normal damage on an attack of opportunity, it is an exception because the norm is dealing normal damage on an AoO.

And Elves have immunity to sleep magic in 3.5 as well, they just state it in the race description instead of the spell. That's just a matter of where it is located because either way the normal circumstances is that sleep will effect a target (assuming he fails the DC) except if he was immunity to such effects (elf racial trait being one way).

Unless I'm missing something, I'm pretty sure those count as exception-based design.

[Murtak]

It all depends on the norm. In your example about doing twice the normal damage on an attack of opportunity, it is an exception because the norm is dealing normal damage on an AoO.

By that reasoning having a Str of 12 instead of 11 is an exception.

And Elves have immunity to sleep magic in 3.5 as well, they just state it in the race description instead of the spell.

Yes, that is exactly the point. If you just put rules in the right place in the right way you can avoid exceptions. By making elves immune to sleep instead of making sleep work differently depending on who it is cast on it you just skip the game parts where complications arise.


2E looks like this:

Code: Select all

sleep cast on (target)
    if target is (Elf)
        do nothing
    else
        sleep

3E looks like this

Code: Select all

Elf
    immune to sleep

sleep cast on (target)
    sleep

And indeed the two are similar for this single example. But the 2E example relies on a special case to make elves immune to sleep while the 3E version has no special cases whatsoever. Everything that happens to an elf gets checked against the list of immunities. Sleep works the same, no matter who it is cast on. And when you get a Deep Sleep spell that still has the [sleep] tag we know it will not work on elves without specifying it (apart from the sleep tag). If we add another race we can also make it immune to sleep effects. We know elves are also immune to drow sleep poison. And most importantly we do not have to remember every special case when designing a new race, spell or effect. We give it the appropriate tags and that's it.

[The Man Who Killed Death]

Alright, I fucked up. I'm retarded, continue with the discussion.

[hogarth]

Why is only exception-based design the one that saves on page-flipping? Can't you have keyword/standardized abilities repeated on the individual entry if you're that concerned about page-flipping?

Sure. And likewise you can have exception-based abilities that still require page-flipping. For instance, the various fog spells in 3.5 D&D: there are cross-references to other spells (e.g. acid fog points to solid fog and solid fog points to fog cloud) and yet there are other fog spells that work slightly differently (e.g. obscuring mist repeats most of the wording of fog cloud, but can be burned away by a fire spell).

[Lago PARANOIA]

Exception-based design saves on page-flipping at very low levels worth of pages total, like if you're playing DragonStrike or HeroQuest.

If you want your game to have any sort of complexity beyond 'I fireball it!' then a unified rules space saves more time in the long run. 3E had a ridiculous amount of material devoted to spells but if it didn't have that section at the chapter beforehand telling us the general mechanics of spells then it would've took up a LOT more space.