I've seen a few posts lately discussing the topic of 'exception based design'; I didn't really look at them too carefully when they first popped up on my radar, but now there have been enough of them to pique my interest.
Tonight I've done a quick Google search to see what it's all about. I had some vague ideas, having done some software programming and web design (where the most common piece of exception based design is making sure a web-page works for Internet Explorer).
I found the following articles/posts:
Whitehall Industries on 'Exception Based Design'
Gamasutra on 'Truth in Game Design'
Most Dangerous Game Design on 'How to Make Games for Everyone'
They each come at the concept of Exception based game design from slightly different angles, but that helps give a better perspective on why some designers choose to use it casually, while others focus on it.
A common case in point is D&D, where the core game mechanisms are fairly vanilla, and every class modifies the rules in some way to reflect a specific range of abilities. In early editions of the game, the combat used a d20, thieves used a d100 for their skills, magic-users had slots of predetermined spells at the start of the day, clerics had quirky rules for turning undead...everyone had their own exception to the rules.
Advanced versions and newer iterations of D&D added further exceptions to differentiate more types of character, and then applied new forms of exceptions in the form of feats and additional rules from supplemental books.
It's an easy way to design, but it's also a lazy way to design...and many other games fall into this trap. In White Wolf's original World of Darkness, there were general rules, but each of the games overlayed a series of specific exceptions, disciplines for vampires (each of which worked their own way), gifts for werewolves (some of which were automatic, other required rolls, or resource expenditure), Mage used a generic and open ended magic system that was unlike anything seen anywhere before...then you had merits and flaws which tweaked the core rules of the game to provide character twists.
Fluxx is all about exceptions, and often how those exceptions interact with other exceptions. It makes for a rich game, but detracts from the ease of playability (especially for casual gamers). When playing a game based on exception based design, you don't need to know all of the exceptions, but the more you don't know, the harder it is to play.
I think this is one of the things that bugs me a bit about the *-world games (Apocalypse World, Dungeon World, Monsterhearts). The differentiating features between characters are all quirky exception based sets of rules (moves) that are overlayed on the core system, many of which work in very different ways. It's a throwback to that lazy style of game design, or maybe not lazy just inelegant.
I know I've fallen into the trap of exception based game design. But lately, in my attempt to get back to basics, I've been trying to avoid it like the plague. Walkabout is the exact opposite, almost everything is resolved in the same way through an interaction between the narrative and a few simple game mechanisms. The names of traits may change, and these changes of name might alter the way they may be introduced into the mechanics through trigger events within the story, but once the traits hit the mechanisms that drive the game it really doesn't matter what they're called...the effects are the same.