Postscript 4 – MoS Counting

It’s somewhat thorny to get an idea of an average numerical value for MoS that includes the possibility of failure, since both failure and an MoS of 0 calculate as zero.  However, if we look at mechanics for using MoS either in cumulative or extended tasks, or when it is used to determine damage or an outcome against an opponent, we can calculate some useful guidelines (and get a window on how to use those values in our game).

There are two prime methods to use MoS in this way.  The first is to have a success (MoS of 0) count as 1, plus 1 additional per point of MoS.  So a success with an MoS of 2 would result in a value of 3, whether that be 3 points of damage/effect, or 3 points added to the cumulative pool towards completing a task or achieving an aim.

Using this, we can determine the average MoS expected for a particular dice pool that includes failure:

An alternate way is to re-work the success ladder presented earlier to make an MoS of 0 a little more precarious by making it a Minimal success:

Thus a Minimal success is a case where the character has just, barely, succeeded at the task.  For example:

• If a character is leaping between buildings, their foot lands right on the edge of the parapet. They made it, but their heart is certainly beating hard now!
• If this leap was part of a chase, it may cause them to stumble a bit, which, depending on how their quarry rolls, might make them lose a bit of ground.
• If the character was attempting to haggle for an item, they only manage to get a minor discount.
• If the character was researching something, they confirm its existence and the overall, general information about the thing, but nothing very detailed.
• If the character was fixing an engine, they get it running in the nick of time, but it was looking dodgy right up until the last moment!

This is opposed to the next rung up the ladder, where a Solid success is an unambiguous one:  a character lands firmly on the roof beyond the parapet; they achieve a worthy discount; they gain a new piece knowledge that will aid them going forward, or they get things running and are sure that things won’t break again.

The value of making a distinction between Minimal and Solid success is mostly one of RP – it’s to narrate a bare success.  It also helps to make each of the levels above a Solid success more distinct and thus easier for the GM to craft mechanical and narratively appropriate outcomes (and thus also more RP-rich).

Minimal success can also be used to tweak the cumulative/damage mechanics by having the value be equal to the MoS, with the special case that an MoS of 0 counts as a value of ½.  This makes things more elegant and straightforward* to calculate as there’s a more direct line between the MoS and the value (when compared to calculating it as the 1 + MoS method above).

Using this Minimal success method, here is the matrix to determine the average MoS expected for a particular dice pool:

*While keeping track of ½ points of success might seem to add back some inelegance, but as the system is already tracking ½ values for the dice pool the context for ½ points already exists.  Much like modifiers described above, it could be recorded using boxes, where a ½ result is marked by placing a single slash in the box and a full point is marked either with an X in the box or by completely filling in the box.

← Postscript – Further Probabilities & Hidden Rolls & Discoveries | Index

So… when I first posted this Part 12 about further probabilities and the “amazing niftiness” of Aurora being bidirectional… I goofed.  Embarrassingly so, and doubly embarrassing for someone who has rolled many a D&D character under good ol’ 4d6 drop lowest.  I very much led myself astray, and I think it was because I became heavily enamoured with the idea/hope that the system was bidirectional, which led me to not examine my probability assumptions.  Mea culpa.

Having finally realized my error, I’ve gone back and crunched the numbers.  Here are the proper, actual, honest, expanding probabilities tables, hidden rolls, and discoveries.

Postscript 2 – Further Probabilities

First, the possibilities for each MoS:

Then the chances of getting at least MoS of X:

Here’s the average MoS expected on a success (if you succeed, this is the average MoS you can expect):

Postscript 3 – Hidden Rolls and Discoveries

Unfortunately, as the above shows, the system is not, in fact, bidirectional.  But some number crunching can get us a little bit of the way there, at least in equivalency.  Here’s a re-written version:

Typically, the difficulty of a task is handled by adjusting the base dice pool.  This allows the player to viscerally feel their chances and properly size up the situation, thus letting them make appropriate choices (and fully RP it out).  However, there are certain instances where it might be more desirable to not “give away” the difficulty of a task to the player and to have them roll blind.  In certain campaign and genre styles – such as one where the characters are expected to be over their heads or one where it is a grim and failure-heavy milieu – this may apply to most of the tests/rolls.  For others, this may be saved for more uncommon circumstances where the level of tension is heightened by explicitly being uncertain and not in the know.

Blind rolling can also be useful for areas like perception, discerning realities, intuition, investigations, and similar, where the GM may not want to tip their hand that something is there (by specifying there is a penalty).  It can be used such that the overall margin of success determines the amount or exactness of the information gained or discovered.  Star Trek Adventures does a version of this for many types of searching, sensor, and similar tests, giving a basic amount of information on a success and allowing the player to spend Momentum (their version of MoS) to give additional and more exacting details and information.  Under Aurora terms, an MoS of 0 would give the base level of information, while an MoS of 1 would reveal something more obscure and an MoS of 3 might divulge everything.

To set an equivalent MoS for a Blind Test, use the following equivalency table:

(Note that these equivalency values change and drop if a character’s dice pool is very high when compared to the MoS required.  For example, a character who has a pool of 7½d and needs an MoS of 3 only actually suffers an equivalent difficulty of -1d instead of the -2d indicated on the chart above.  This is unlikely to have a major impact in most scenarios, but if a character’s pool is large and gauging against a low MoS equivalency, consider stepping up the required MoS by one if you’re finding characters succeeding more often than expected and appropriate for the campaign.)

← Postscript – Breaking the Core Mechanic | Index | Postscript – MoS Counting →

As I noted a little while back, our group has delved into the Cortex Prime ruleset for our current campaign.  I’d tried out Cortex a bit in Firefly, but this is my first deep foray into the system and thus far I’m really liking it.  There’s a lot to it that does a good job of facilitating a narrative-heavy style of play, with each character having plenty of latitude to accomplish things in their own way which helps make them feel distinct, interesting, and open for lots of RP.  Good stuff!  And that the first “complete” Cortex Prime RPG has just been released (as opposed to the Cortex Prime rulebook which is a giant toolbox) in the form of Tales of Xadia there’s plenty more chances for people to try out the system, and I’m excited for its spread.

However, there is one aspect of the system that threw us a bit for a loop:  Generally, building a larger pool* is desirable as, obviously, makes it more likely to get a high result and thus achieve success.  Perhaps counterintuitively though, that same larger pool also means more chances to roll a hitch and therefore more chances for a complication.  Thus, the better your chances equally better is your chance to have something detrimental come out of it.  This seemed both weird (in that counterintuitive sense) as well as punishing, and we bumped on it for a while.  However!  In yet another one of those “walking through the house” epiphanies, I got what I was missing to see it in a much more useful light:

1. Rolling a hitch always removes the die from your pool. However, AND THIS IS THE BIG THING, it is up to the GM whether to ‘activate’ it as a complication, or not.  Not every hitch HAS to be activated into a complication.
2. IF the GM activates, you get a PP. This is important as it is one of the primary ways to enable and ensure the meta-currency economy.
3. So if you do get the complication you also get something to help you get out of it if you need to… and if you don’t, excellent! You get to save that meta currency for extra awesomeness later.
4. In addition, if the GM creates a complication based on the hitch, then, in general, that complication should LAST NO MORE THAN THE SCENE. It mucks things up in the moment, but it isn’t “sticky.” They are a narrative setback that are a niggle only for the moment.  (Lingering and sticky effects should mostly be the result of a failed test or contest or go to the stress track if using that mod.)
5. (As an aside, if there is a case where it might be good to include a complication as something that lingers, then it can act like a clock, filling up until it triggers something. For example, a hitch on a test to infiltrate a facility could begin a complication called “Compound Alerted”, which might increase the base difficulty of future tests, and if the complication is stepped up above a d12 then compound goes onto lockdown.)
6. It is also good to remember that complications don’t necessarily apply on every test going forward, only on tests where the complication would apply or have an impact. This can entice players to find alternate and creative ways to work around the complication, leading to more drama and dramatic action.
7. Overall, the intention behind this mechanic might be to “balance” large pools somewhat. In other words, if you can build up a big pool the increased chance of hitches helps keep it in check and keeps things narratively interesting.
8. I think a good hitch activation rate might be between 1/3 to 1/2 of the time. This allows for the narrative drama without it becoming a frustration for the player or, worse, feeling feel like punishment for when your character is really good at something (ie, when you have a tonne of dice in your pool).  It also alleviates the GM from having to continually come up with interesting complications.
9. (For clock-like hitches it might be OK to activate them more often…)
10. It’s also worth thinking about when to step up an existing complication, and when to create a new one. Roughly, I think stepping up only once per scene (which keeps it from potentially becoming overwhelming) is a good baseline before activating a new complication.

As an additional bit, and I don’t know if it’s explicit in the Cortex Prime rules or not, but I would allow the players the choice of whether to include an opponent’s complications or stress dice in their pool or not.  If they are forced to, and they hitch on that die, then once again it can elicit frustration and annoyance.  Alternately, or in conjunction, as a GM I’d have a light touch on activating complications that arise from including an opponent’s complication or stress dice in the player pool.

With all of the above in mind now this quirk of the system sticks less in my craw.  It becomes an opportunity for something, and like so much else at the table it is an opening for conversation.  What would be cool here?   What would make for the “best” story?  What’s dramatically appropriate?  Out of that will come whether or not to create a complication and, if so, what complication to create, all in service of the action and drama and story.

* Briefly, if you’re not familiar with the system, the base mechanic is to build a pool of dice (of differing sizes depending on what’s going into the pool), roll, and keep two to determine your total.  Any die that rolls a 1 is not only removed from the pool but, crucially, allows the GM to create a complication for the character.  These complications come with their own die rating and actively hinder the character.