SM Probabilistic System

The PROSYS Overview
This is not a game of chance. If someone wants a game that lives by chance, we recommend Vegas. They have plenty of chance – and it's all stacked in favor of the house. It's a romantic notion to live with the odds, but it means the "live" part will be short. This is why people who want to accomplish the mission, train for the mission.

"The more you sweat in training, the less you bleed in combat."

Unlike systems where skill modifies wildly random chance, PROSYS is about applied, consistent capacity. Don't worry, the Universe finds ways to add chaos to the attempt – and we call those ways mods – but we start with what we can control: our character's skills.



PROSYS Introduction
As a resolution system, PROSYS is staggeringly easy:

1.) Compare a task's Degree of Difficulty (DoD) to the character skill.

2.) If the skill is higher, the task is successfully accomplished.

A game could theoretically be run on this principle alone. Of course, the world isn't that simple and PROSYS wouldn't be much of a simulation if it assumed every attempt was made under laboratory conditions. That's why we introduce the devil: the details – all the factors outside player control that complicate the task. In the PROSYS, the details are expressed numerically as modifiers – or "mods" for short.

The mods account for most the Clausewitzian factors of friction, what some folk know as the Fog of War. Even when we do our best to quantify everything that could affect a player, there are still elements of Volatility, Uncertainty, Complexity and Ambiguity. Some folk lump those together as VUCA, but we just call it luck. While this isn't a game of chance, we still account for those ever-present randomizing factors.

PROSYS In Practice
Interpreting the results:
 * 1) Determine Task DoD.
 * 2) Apply modifiers.
 * 3) Apply luck.
 * 4) Compare against PC skill (or applicable trait).
 * If the skill matches or exceeds the mDoD, task accomplished.
 * If not, task failed.

No amount of skill can prevent faulty batteries, untied shoelaces, sneezes, allergic reactions, dexterity errors (the common "whoops" can kill you), sequence errors (you don't even have to be stressed to forget a step), mental fatigue, metal fatigue, frayed straps, micro stress-fractures, exposure-related degradation, manufacturer defects or twenty-five other ways to induce equipment failure.

Not all luck is bad luck, but good luck finding good luck. Manifestation is the key, and this is where some random numbers come to play. The effects of chance are usually small in comparison to the overall probability, but they can make all the difference. In some situations, even a success can undermined by a little bad luck... and sometimes a failure can turn into a success for the same reason.

Once the DoD has been modified and luck applied, it goes right back to the elegant simplicity of the PROSYS system. If the character's modified number is higher, the player is successful. If not, the player needs to back up and try again or think about a different tactic.

Look Before You Leap

 * People can usually guess their chances, but it doesn’t always mean they’re right. Refs will the give an appearance estimate to the category (not the exact number) – and that will probably be accurate, but unseen factors that affect the complexity of the task may affect how it looks – making appear easier or harder than it actually is.

The Art of Faking It

 * Good heavens! What if your character doesn’t have a required skill? Well… what would you do? Often the subject of nightmares, there are alternate ways of thinking through a problem. Improvising requires Attribute comparisons and semi-related skills (if any).

Getting Personal

 * A few situations will challenge the very fabric of a character. In these circumstances, the Task DoD may be compared directly against a particular trait. In some situations, specialized skills may be called into play that give the character a bonus. These skill are usually lower in number than typical skills to reflect the nature of the knowledge. If you think this sounds a little ominous, you're right. Stay tuned.

(2) Apply modifiers.
Think “friction”: the cumulative effects of uncertainty, suffering, confusion, exhaustion and fear. Who gave us this bubbly observation? Prussian strategist Karl von Clausewitz, who was helping the martial academics of the time to realize that warfare couldn’t be simplified to a few equations.

Anything that can go wrong, will.

Under PROSYS, modifiers (henceforth referred to as “mods”) are numerically quantified factors that influence a task’s DoD. Mouthful, eh? Mods are applied cumulatively, and while not all of them are bad… most of them are. In fact, the British Army had their own summary of friction; they called it “Murphy’s Law.”

Add the appropriate mods to create the modified Degree of Difficulty ("mDoD").

PROSYS Modification Categories

 * Arbitrary time limits
 * Performance under fire
 * Pain
 * Exhaustion
 * Confusion
 * Inclement weather
 * Concentration
 * Improvising
 * Assistance

(3) Apply luck.
"'There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.'""~Donald Rumsfeld"Got luck? It's always there, even if it's not a visible factor.

Even in the most controlled situations, there is a random element from factors not accounted for. Robust systems are built to compensate, they counter against flaws with redundance. They're built to have high fault-tolerance and high thresholds before failure. Likewise, if people are pushing their own personal thresholds, the smart ones take steps to help their chances.""

Luck, quantified:
On every task, a player will roll d10 to determine the influence of uncontrolled factors. Even numbers will add good luck. Odd numbers will subtract bad luck.

Luck can quickly cascade: a roll of "1" will cause a second roll where the number (odd or even) becomes a negative modifier. Conversely, a roll of "10" (a "0" on the die) where the number (odd or even) becomes a positive modifier.

On a second roll of "1", roll a separate d10 to add this level of consequence, then roll to check for the third level. This can continue up to 5 times: a maximum of 50 points of luck, either catastrophic or miraculous.
 * On isolated tasks, where the character has [apparent] complete control of the situation, only the player will roll.
 * On actions that directly and immediately affect the player, but aren't caused or controlled by a player action, the Ref open rolls (visible to the player) d10 to see if anything happens to affect a given task.
 * On actions that are opposed, luck will likely affect the opponents differently. The Ref will make a simultaneous roll for the NPC, which may be good luck or bad. Note that opposed luck rolls that are bad for the NPC may be good for the PC, but that's not guaranteed. Bad luck on the grenades fuzing system may be bad for the PC, too. And vice versa...
 * For actions that happen in the background, the Ref will make hidden rolls.

Luck, qualified:
Most lucky breaks can be forgotten as soon as they’re applied. In certain circumstances, more significant events will be quantified by the ref (and may come to play later). Bad luck doesn’t necessarily mean task failure: it’s all about skill level beating the DoD, remember? Still, even if the player successfully completes the task, bad luck hangs on. In fact, the player had a small influence in exactly what happened: an even unlucky mod indicates equipment failure (or third party); an odd mod was a character mistake.

Minor problems (<10)

 * Batteries die, straps come loose and fingers slip. The key to the airport locker is bent.

Major problems (11-20)

 * Straps break, hands slip, sand gets in the eyes. It uses metric and you've only got standard. The key breaks in the lock.

Catastrophic problems (21+)
Luck affects per attempt, and barring depleted resources (gas, bullets, explosives, White Out™), et al., one failure doesn't rule out a second attempt. If characters have the luxury of time and equipment, take another shot. Since the player is, in effect, the spirit of the character, I wouldn't rule out bribing the Ref either (I Ref a lot).
 * Carabiners, D-rings, or buckles break – while they're being used; Feet slip, batteries explode. The broken key is jammed in the lock.

Luck, Equal Opportunity
There is one other blessed factor of luck, and it has nothing to do with the player's characters: it has to do with the scenario's characters. Murphy will strike the bad guys just as much as it does the good guys. Refs shouldn't forget that when keeping tabs on the antagonists.

Luck rhymes with...?
Luck is fickle, and while skill can’t negate bad luck, it can compensate for it. Bad luck that falls under the character's skill level means they handled the bad thing without consequence.

Resourceful PCs also create realistic backup Plan B, C, and maybe D, too. Think of spares, redundancies, and always telling the ref that you’re taking such steps. It might not be Cool Cavalier to do so, but nobody invites a dead guy to a party…

(4) Compare against PC skill (or applicable trait).

 * If the skill exceeds the mDoD, task accomplished.
 * If not, task failed.

Sweeping Gesture vs. Miring Minutiae
The amount of work completed in any single task should be appropriate to the game situation and pacing. A task could be the singular act of picking a lock, or include as many complex steps as rebuilding that jeep engine. The idea is that a task is a single, definable, progressive step in the game.

Here's another way of looking at it. Besides initial preparations, the characters are going to have to go somewhere before they can do something. It is probably more appropriate to sum up average travel by making a few comparisons of geographic knowledge and language skills than attempt an intelligence check for each specific step.

If the goal of the game were to change, however, to include travel as fundamental part of the process, then you'd get more specific. When would this happen? Maybe if the characters were in an escape and evasion sequence, or perhaps a search and destroy mission against a fleeing target.

The dangers of imbalance in tasking are dual. First, making the process too incrementally complex will. . . slow. the. game. into. tedium. Second, beware of over-simplifying things. Making one big comparison of character skill takes player decisions out of the equation. Suddenly, the whole soul of the PC entity has no chance to actually experience and affect the situation. Witness the following situation…"'Hey, Bob!'""'Hey, Tom!'""'Say, my character has an adventure skill of 100!'""'That's great, Bob! You've saved Boston from nuclear disaster. How 'bout those Bears?'"…Lacks, something, doesn't it?

On the other hand, if you’re up for a high-octane variation on the PROSYS, try a “speed game”. These Probability beasts dispense with every mod: either the character succeeds or fails.

If you want fast, but not break-neck (and a little suspense), add only luck rolls.