Here we are with part three of the style guide. It might seem as though rules and mechanics are entirely a game design issue, and that a “style guide” to writing rules would be unnecessary. On the contrary, I think it’s particularly important. It can be easy to get sidetracked from writing issues when working on rules.
Mechanics (Rules, Powers, Abilities, Rituals, etc.)
Atmosphere & Genre: Make sure your mechanics promote and are consistent with your atmosphere and genre. Mechanics can do a lot to promote (or take away from) the atmosphere of a game, so consider them carefully.
Balance: Power-balance things where appropriate within the structure provided by the game.
Clarity & Simplicity: Keep your mechanics write-ups clear, simple, precise, and specific. If they get too long and you can’t find a way to shorten them, consider that you might need to alter the basic mechanic.
Concrete Details: When writing up rules it’s easy to get sucked into writing theoretical, abstract material, which is harder for people to read at length (and harder to assimilate). Come up with ways to work concrete details into your rules, even if it’s simply through the use of examples.
Consequences: Consider the consequences of putting such a power or mechanic in the game-world. What does its presence imply? Think about how it would have interacted with the game world in the world’s past, and think about how it would impact other people’s games in the future.
Consistency of Atmosphere: Make sure your rules, powers, etc. back up and promote the kind of game you’re encouraging. If you’re writing a game about scholarly sorcerers then it’s counter-productive to create powers that are almost entirely combat-oriented, for example. Similarly, you wouldn’t write up lots of silly-sounding items for a creepy game of horror.
Consistency of Mechanics: Be consistent in how rules and die rolls work. Individual mechanics can vary, but the ways in which they work should be consistent. (E.g., if one set of die rolls has an automatic success condition, then all die rolls should have an automatic success condition.) This makes it much easier for someone to learn and use a new set of rules. It also cuts down on confusion.
Cure-Alls: Try to avoid cure-alls and quick answers to problems. Most things that instantly solve serious problems should create other problems for the PCs to deal with, or should be difficult, one-use-only, rare, pricey or dangerous.
Customization: Try to provide suggestions to help game masters (GMs) customize the rules, powers, etc. to suit their particular game and players.
Effect: A single stat, ability, or mechanic should not have a disproportionate effect on the game. (E.g., you don’t want small variations in one character stat out of 10 to single-handedly determine the outcome of combats.) Playtest your mechanics in order to avoid this.
Examples: Use examples to clarify complex rules. Often one well-made example can clear up a host of questions.
Extremes: Try to avoid the possibility of too many extreme results when a mechanic is used. It’s good to make sure that extreme results are possible, but they should not happen too often (this is somewhat genre-dependent, however).
Feelings: Always consider how the players will feel if this power, item, etc. is used on their characters. If the answer is frustrated, angry, cheated, or some similar variant, then consider re-writing. “It will never be used against the player characters” is the wrong answer — you simply can’t (and probably shouldn’t!) declare or predict how it will be used in other people’s games.
Fine-Tuning: Beware of fine-tuning too much–this is where rules tend to expand out of control, or become workable only for your own group of play-testers. Try to keep things simple and straightforward. If necessary you can always provide guidelines to help GMs fine-tune things for their own games.
Format: First, provide a brief, concise, clear wording of the main rule point. Then you can add details, explanations, corner cases, and examples.
Game-Play: Try to encourage useful game-play with your powers, items, and rules. Take party-play, hooks for further plots, the needs of the game structure, and so on into account. Don’t put things into the game that will, for example, sideline players for a long period of time.
Instant Death: Try to avoid instant-death powers on general principle–they aren’t much fun. If you simply must include one, make it particularly difficult, dangerous to the wielder, unlikely to work, one-use-only, or in some other way extremely unlikely to get used more than once. (See the sections above on Feelings and Cure-Alls.)
Low Level: Try to provide lots of simple abilities that are useful but not overly powerful (where appropriate). These should be more prevalent than high-powered “nuclear” abilities. After all, remember that all characters start out at low level, and not all of them will reach high level. This implies a greater need for low-level abilities. (Do remember that the definition of “low level” is game-dependent, however. A power that would be considered low-level in one game would be high-powered in another.)
Narrow Scope: The narrower the scope and the more specific the use of your “powers,” the easier they are to power-balance, provide plot hooks for, etc. Just remember that if abilities are narrow and low-powered, they shouldn’t be particularly expensive and hard to use, or people will never play with them. (This suggestion, however, is particularly game-dependent. Some games work well with simple, broad powers, and they’re appropriate to some genres.)
Phrasing: Make sure everything is clearly stated in terms of its mechanical effects, as well as any more “fluffy” statements.
Player Characters: Always take the PCs into account. What would happen if the PCs learned the ritual, got the item, or developed the power? If the answer is “bad things!” then consider re-writing. Nothing should be written with the assumption that only non-player characters (NPCs) will use it.
Plot Hooks: Mechanics should (where appropriate) include, promote and suggest plot hooks, back-story, and atmosphere. This inspires readers and makes the GM’s job easier, which makes him more likely to play your game.
Start with Characters: If you’re having trouble getting inspiration, start with some interesting characters and think about what you would want them to be able to do. This can be a good way to come up with powers, items, abilities, and so on that players will actually enjoy.
Use: What is each power useful for? Is it interesting? Practical? Fun? Atmosphere-promoting? Make sure there’s a reason and a purpose for each power and mechanic you create, even if it’s a simple one.
Variety: Make sure there’s plenty of variety in your powers (where appropriate). This makes the game fun for a wider variety of players. It makes the GM’s job of creating a variety of NPCs easier. And it makes it more likely that people will enjoy playing your game over and over, because they’ll have plenty of fodder for coming up with new and interesting characters time and time again.