Flexible Systems
One of the bigger mechanical changes in 4E is Saving Throws. Rather than treat it as a unique mechanic onto itself as previous editions did, it's been combined into the standard defense mechanism. So Reflex, Fortitude and Will are just different flavors of Armor Class, providing four different defense stats that all work the same way.
Whenever a character does anything attack-like, whether swinging a sword, breathing fire, or subverting someone's mind, the player rolls an attack against one of these defense stats. And these numbers scale up like everything else.
This is a good example of a standardized system that allows easy adaptability. If the DM wants to invent a new monster attack, or a new trap, or even improvise a new action in the middle of a game, it's fairly easy to determine how to resolve it. Generally, roll an attack or ability and compare it to one of these defenses.
Having four defense stats means it's easy to generate attacks that feel unique and different but operate on the same basis mechanically. And by exposing the underlying math, a good DM knows how to generate unique content for each encounter and to adjudicate when something strange comes up, which it usually does.
This doesn't all translate directly to video games, since we lack a DM at the table to interpret these rules real-time, but it does give some good guidelines for feature and content design. Create systems with enough flexibility to cover a wide range of real situations...Make sure the mechanics emphasize the differences between situations rather than flattening them all out to be the same...
