First and foremost, STORM is not a game, it isn't even a game system. STORM is a basis for a system, a framework upon which you'd build a game system. It is a system for defining how to resolve contests. It's an outgrowth of a system (NAGS) I originally wrote due to my dissatisfaction with the original Amber Diceless system by Eric Wucjik, and as such, inherits some of the same sensibilities and design goals as the Amber system.
For those of you familiar with the terminology developed by Ron Edwards, this mechanic is Karma-based, though it does include the option to throw some Fortune into the mix. That means it works similarly to the way that the original Amber DRPG system works, each trait the character has is rated, and when a contest arises that's governed by a specific trait, the person with the higher trait will win, barring unusual circumstances.
In STORM, characters are defined in terms of their traits. What traits a character has will vary from game to game. In many games, these will be a list of basic physical and mental capabilities, along the lines of Strength, Dexterity and other old familiars. For other games, the traits may include aspects of trained or learned skills, such as a pirates and swashbuckling game which includes Swordfighting and Panache as two traits.
Similarly the scale traits are ranked on will also vary. Typically, but not always, the traits will be ranked numerical, with higher ratings being a better ranking. Typically a range and average are specified, such as from 1 to 20, with 10 being an "average" normal human. But that's not the only possible scale. For a game where the characters are much better than a normal human, the same 1 to 20 scale might make 1 a normal human, leaving plenty of room above it for superheros and the like. The scale can be as big or as small as necessary, a superhero game might instead make the scale 1 to 1000, with 10 being average human.
For purposes of the rest of this document, we'll assume a scale from approximately 1 to 20, with 10 being human average and say... 18 being the typical human maximum, and the same traits as one of the more prevelent existing systems:
Again, these aren't meant to indicate that the STORM mechanic should only use these traits on this scale, merely that for the rest of this document, we'll assume the overall gaming system uses them, so we can make more concrete examples.
At the most fundamental level, the mechanic involved is very simple. A contest is defined in terms of a trait which governs the contest. The person with the highest trait, wins.
If two people are armwrestling, and one has a Strength of 15 and the other has a Strength of 12, the one with the 15 wins.
That's it. It's really that simple.
Well, okay, not entirely. STORM has two features which make things more interesting, Synthetic Traits and Compound Contests.
Synthetic Traits are those that are composed of aspects of two or more basic traits. Some contests might actually be as simple as a one trait comparison; the above armwrestling contest, for instance. However, many athletic endevours require skill and agility as well as power, so it makes sense to factor in Dexterity; by averaging Strength and Dexterity you could better handle a high jump competition for example. Average in a third trait, Constitution, and now you can cover a foot race, where you also have to maintain performance for a period of time. Some contests might even be best resolved by averaging all the basic traits a character has.
However, traits aren't always equally useful for a contest, so sometimes you want to weight them appropriately. A marathon might be 3 parts Constitution, and 1 each of Strength and Dexterity to represent the various aspects that affect the race's outcome.
As another note, the traits compared don't have to be the same on both sides. For example, during a sword fight, you might consider average Strength and Dexterity to represent a sword attack, while the defender uses Intelligence and Dexterity to spot the attack and correctly parry it. In fact, you don't even have to use the same number of stats. If the above sword attack were a simple attempt to knock the defender over with a shield using pure Strength, the defender could still try to deflect the attach using the average of Dexterity and Intelligence.
As a quick math note, doing lots of division for averages is tedious and error prone. ("Math is hard, let's go shopping.") As long as you're comparing the same number of stats, you don't have to actually do the division, just compare the totals, and the result will be the same. However, if the number of traits, or parts of traits if you've got a more complex formula, isn't the same it's generally best to do the division, so both results are on the same scale. It's a bit obvious, but easy to overlook in the heat of climatic scene.
Another straightfoward, but easy to forget, thing to do is to precalculate various commonly used composite traits. If you find yourself constantly averaging your Strength and Dexterity to use during sword battles, write it down. Or come up with a new trait name; in this case Athletics might be appropriate.
The other interesting major aspect to STORM is decomposition. Just like you can compose a more complex contest by using several different traits, you can decompose a single contest into a series of smaller, simpler, contests. Most contests aren't actually resolved based in one instant, there's a give and take as each side jockeys for advantage using their best traits to their advantage. As a game mechanic, this works quite simply. For contests that are less important, it's fine to make a single comparison and be done with it. But for contests that are important to the story, either because they're critical to the plot or they're simply approrpriately dramatic, break down the contest into a series of smaller sub-contests.
In the simplest form, this is a 'tie-breaker' trait. For example if two people arm-wrestling both had the same Strength, then the winner would be who could last the longest, the person with the most Constitution. If their Constitutions were identical, it could fall over to Wisdom, the person with the most stubborn desire to win.
In a more complex example, a heated debate between two lawyers will determine the fate of a critical aspect of the plot (whether one player goes to jail), so the contest is broken down. In the first phase, the prosecuting lawyer presents factual evidence, drawing on his Intelligence skills, and the defender chooses to grandstand, using his Charisma to win over the jury and the judge. The next phase starts with prosecuter using his Intelligence again, and the defender, realizing his antics aren't working, uses Wisdom to object and disrupt the arguments of the prosecutor. This continues on until the end of the trial, with the various successes and failures of each side adding up to determine the outcome.
With careful selection of traits, and appropriate use of Synthetic Traits and Compound Contests
So far, no mention has been made of any possible outcomes besides win or lose, though for many contests, ties are a valid outcome as well. However, often times things aren't so clear cut. In some cases makes some sense for the degree of victory or success to depend on the relative rating of the traits being compared. If the difference is larger, the degree of success is larger. Simple and intuitive, isn't it?
Relative success is also useful for extended contests. The degree of success in one sub-contest can be applied as a mitigating factor in the subsequent contests. For example, using a hypothetical sword fight, if the first contest is a sword attack versus a parry, and the parry wins by a large amount, in the next contest, the person who parried will have a bonus to their trait, representing the advantage they earned for their superior parry.
Oftentimes contests don't happen under the most ideal of circumstances. Here's a list of ideas for things that might alter a character's effective rating:
The degree that these affect things will depend on the scale that traits are ranked on. For a typical 1-20 scale, no single factor should probably be worth more than one or two rating points. Depending on the genre of game and the scale, it might also make sense to have a cap on the maximum advantage or disadvantage from outside factors. In a Superhero game, for example, it wouldn't do for a hero or villian to go to an early grave just because a bunch of factors added up wrong for them. Similarly, in a gritty and reasitic jungle warfare game, it might make perfect sense for the factors to be effectively more important than the character's ratings.
If the sides of a contest are sufficiently close in their trait ratings, it's entirely possible that someone with a lower rating could actually win. Usually this comes as a result of other factors, like the sort mentioned above, but going into that much detail can bog down the flow of the game and turn a pulse pounding scene into an excercise in number crunching. In these situations, it's often fine to use some randomness to simulate the net affect of these factors on the results. Here's one possible rule of thumb, assuming traits are rated on a scale of 1 to 20:
As it turns out, this can be pretty easily simulated by adding the result of a d3 to the trait (or a normal six-sided die, divided by two, or a Fudge die, if you happen to have one of those lying around). If you have a bigger scale, or the difference between rankings is smaller, use a die with more sides, or even multiple dice. Or, if your group likes the idea of going without dice, the players (including the GM) can just choose to resolve these close contests on a case by case basis.
Note that using randomness doesn't mean that characters can't get normal modifiers for deliberately engineering things in their favor. This is meant to cover all the 'background' factors that you'd otherwise have to consider, or uncertain circumstances where luck becomes a larger than normal factor. This means you can also tailor things depending on the uncertainty of the situation. Two people dueling in a formal tournament will have very low uncertainty, perhaps none at all. The same two people duelling on a crumbling cliffside over a pit of boiling lava, in the rain, at night are going to have alot of uncertainty. In the first case, a die with a small number of sides might be right (maybe two or three sides), the latter, a much larger die (maybe an 8 or 10 sided one) or multiple regular dice could be appropriate.
So far, STORM has only dealt with traits. This is because inherently, it makes no differentiation between what would be a trait and what would be a skill or a talent. In some game systems, the traits might well include those that deal with both learned skills or practiced abilities. For example, the original Amber Diceless system had Warfare, which covered not only tactical and strategic thinking, but learned skill with weapons and the knowledge to lead armies and win battles. Under other gaming systems, that would covered by several basic traits and a number of seperate skills.
There are basically two ways to handle skills in STORM, decoupled and coupled.
When using decoupled skills, a skills is treated like any other 'basic' trait. It has its own rating and can be used to create composite traits just like any other basic trait. The advantage to this method is that skills don't require any special handling, they're just another trait. The downside is that skills are just like traits, and can overwhelm the importance of the basic traits, which may not be desired.
This method works best for games and genres where which skills and how good they are can make a big difference during a contest, or where a fairly large number of exotic skills are in use. For example, a Superspy game might work well this way, as the abilities of various agents can vary widely, and those skills can turn a person with only decent basic traits into a force to be feared. Genres that rely on having acess to bodies of rare knowledge, such as occult horror, might also be good canidates for this method.
When using coupled skills, the traits remain the basis for any contests, and the skill is treated exactly like any other mitigating factor, adding to the end result of the contest. When using this style of skills, it's often best to make the advantage the skill gives dependent on how specific it is and how appropriate to the situation. A very specific skill used in the right situation is more useful than a general skill in the same situation or using a skill that's merely related to the situation. The primary advantage to this method is that it can easily adapt the benefits to the contest at hand and cover things like "gifts" which don't necessarily work well as a normal trait.
This works best for genres and systems where the characters can be expected to be of approximately uniform skill level, except in certain fields, where they shine. Amber and Superhero settings, for example, where the characters can be assumed to simply be 'proficient' at everything and the skills that are important are those so noticably above average that they give a special advantage. This also works well for very mundane settings, where everyone will have the same basic knowledge and proficiencies.
Another thing implicit in STORM so far is that contests are always between two characters in some form. There are several reasons for this, the most fundamental of which is that inter-character conflict is the most interesting and least predictable from a game standpoint. However, in many games there will arise situations where the character is faced with an impersonal problem. Some of these can be turned into a character conflict, for example a trap could pit the skills of the trap designer against the wits of the character who potentially triggers it. But somethings just can't be view that way; for these, it's up to the GM to set some sort of target number, based on the relative difficulty involved, just like for any other system mechanic.