Mechanical Hooks

While I appreciate and enjoy games with focused or streamlined rules, I get so much enjoyment from complex systems with many moving parts. I like games that have a lot of rules that interact in different ways and reward choices as a player as well as decisions made in-character.

I think of mechanics in these games as hooks, and the interactions between them are strings tied around these hooks. The more hooks a system has, the more connections can be made between them. The result is an exponential increase in theoretical complexity, but a good design will limit this creep by only exploring some subset of possible interaction.

The easiest way to reduce complexity is to set aside one or two types of hook as open to referencing many others, while the rest can't. In this way, as the number of hooks increases, the rise in complexity is more linear than exponential.

Here are a few examples of systems rich with mechanical hooks.

Fate

The most obvious hooks in Fate are character traits: aspects, skills, stunts, stress, and consequences. But due to the Bronze Rule (also called the Fate fractal), these traits can exist on just about everything, from objects to locations to scenes. So, a trait on a character can exist independently of the exact same trait (say, a particular aspect) on a piece of equipment.

Even beyond character traits, there are some areas of the system that can be hooks: milestones (the pacing of story content that also impacts character advancement); units of narrative (scenes vs. sessions) independent of their value as milestones; active versus passive opposition; and so on.

For the most part, the one trait that can really leverage the other hooks is stunts. How stunts trigger and what effects they have can reference all of these. Most stunts tie directly to skills, but examples exist of stunts that change how aspects are invoked, how stress is gained and lost, and how consequences are earned or recovered. Stunts can be limited by scene or by session, they can require fate points, and they can trigger off of any fictional or mechanical state.

Dungeons & Dragons 5e

We start again by looking at character traits as hooks. A character has race, sub-race, class, sub-class (whatever the particular class calls it), background, proficiencies, ability scores, alignment, current and maximum hit points, Hit Dice, etc. Optionally, characters can have feats, and they can multiclass. 

Monsters have many but not all of these hooks as well. In addition, monsters have traits and descriptors of their own, such as creature types and subtypes, or even particular actions and attacks. With the introduction of lair actions, the environment around the monster becomes a hook.

The states of advantage and disadvantage are hooks. Possession of inspiration is a hook, as is spending it to gain advantage or give inspiration to another character.

Class features (such as a rogue's sneak attack), feats, spells, magic items, and more can all leverage many different hooks. D&D 5e has the potential for incredible complexity even before the first supplement is released.

GURPS

Few GURPS mechanics reference the presence or absence of any other hook in order to have a compartmentalized effect. Instead, if a mechanic interacts with a hook, it will tweak the normal rules for that hook, with potential knock-on effects in other related systems.

For example, when a character takes damage, they normally suffer a penalty to rolls on their next turn. If the character has the High Pain Threshold advantage, however, they ignore this penalty. Low Pain Threshold doubles it.

Advantages provide bonuses to skill rolls. Skills can alter the way Fatigue Points replenish. Losing FP or HP can affect skill rolls, movement, and defense in combat. The maneuver you choose in combat limits your ability to move or defend. The effects of an attack differ based on the victim's maximum HP. The list goes on and on.

GURPS actually suffers from allowing too many hooks to leverage other hooks, rather than keeping to one or two categories (just advantages, say). Many interactions are optional, even if that means restricting the availability of certain traits. The fact that so many hooks exist and the interactions are possible means that the system looks incredibly complex, even if the execution in any particular campaign is not.

Conclusion

Systems with a lot of hooks can be more or less complex based on how interactions are managed. They can seem more complicated than they are based on presentation. And ultimately, greater complexity is not always a good thing. While I enjoy many baroque games, they are not always to everyone's taste.