Tell Me About Cortex Prime

[Staffan]

I think it would probably be more helpful to look at a specific example, so you can see what it is doing that Fate does not. And I enjoy Fate, it also does thing Cortex doesn't.

Marvel Heroic Roleplay is actually Cortex Plus, which a half step back mechanically, but still a good example.

One thing I noted with Marvel Heroic compared to the suggestions in Cortex Prime is that Marvel will often have bigger dice pools.

The default in Cortex Prime is that the game you're building will have two "prime traits", or two sets of traits that will be the usual thing you're adding to a dice pool. This could be something like Attributes + Skills, Attributes + Roles, or Skills + Relationships. In addition, you have Distinctions, which sort of serve the same purpose as Aspects in Fate: they are true things about your character, and if you can use them to your advantage that's a d8 to your roll, but if they're a liability you instead add a d4 and get a plot point as compensation (remember, any 1 on a die is a "glitch" which both causes some trouble and makes that die useless for that roll, and 1s on d4s are pretty common). So most rolls will have 2-3 dice in your dice pool (depending on whether you can squeeze a distinction in or not). You need to use two dice for actual success, and if the thing you're doing uses an effect die that's a third die. So that doesn't give many options. You can get extra dice from Assets or (depending on rule variants) opponent stress/complication dice, but those aren't always there to be used.

But in Marvel Heroic, characters will often be able to bring a lot more dice to bear. You can often bring dice in from multiple power sets, and you also have specialties (sort of like skills). So if, for example, the Black Panther was trying to covertly infiltrate a place he'd roll something like:
Solo d10 + Peerless Strategist (distinction) d8 + Wakandan Technology: Wallcrawling d8 + Chosen of the Panther God: Enhanced Reflexes d8 + Covert Master (specialty) d10. That's five dice, which gives a lot more room for dice shenanigans than the two or three you'd normally get.

 

[RivetGeekWil]

The default in Cortex Prime is that the game you're building will have two "prime traits", or two sets of traits that will be the usual thing you're adding to a dice pool. This could be something like Attributes + Skills, Attributes + Roles, or Skills + Relationships. In addition, you have Distinctions, which sort of serve the same purpose as Aspects in Fate: they are true things about your character, and if you can use them to your advantage that's a d8 to your roll, but if they're a liability you instead add a d4 and get a plot point as compensation (remember, any 1 on a die is a "glitch" which both causes some trouble and makes that die useless for that roll, and 1s on d4s are pretty common). So most rolls will have 2-3 dice in your dice pool (depending on whether you can squeeze a distinction in or not). You need to use two dice for actual success, and if the thing you're doing uses an effect die that's a third die. So that doesn't give many options. You can get extra dice from Assets or (depending on rule variants) opponent stress/complication dice, but those aren't always there to be used.

One thing to note...distinctions are a prime trait set and are assumed (and highly recommended) for all Cortex games. A distinction will be included in every roll. If for some reason a distinction doesn't quite fit the fiction, hinder one of them instead. If it often occurs that no distinction is really fitting for what the character is doing, you have a problem. Either the distinctions are out of tune with the game's situations, or the game's situations are out of tune with how the characters were built. You need to change one or both. It's also super important to remember that the player decides when to hinder a distinction. They don't have to justify it. They just roll a d4 instead of a d8 and get a plot point.

"Plus sets" are only added when they are relevant. Most Cortex Prime games have 3 prime trait sets (Distinctions plus two others) and 2-3 "plus sets". All applicable signature assets, created assets, and complications can be added to a pool. Because of this I very rarely see pools of only three dice. While it's not typical, I've seen 8, 9, and even 10 dice in a Cortex Prime pool.

 

[Thomas Shey]

But in Marvel Heroic, characters will often be able to bring a lot more dice to bear. You can often bring dice in from multiple power sets, and you also have specialties (sort of like skills). So if, for example, the Black Panther was trying to covertly infiltrate a place he'd roll something like:
Solo d10 + Peerless Strategist (distinction) d8 + Wakandan Technology: Wallcrawling d8 + Chosen of the Panther God: Enhanced Reflexes d8 + Covert Master (specialty) d10. That's five dice, which gives a lot more room for dice shenanigans than the two or three you'd normally get.

That's part of the key; MH assumes powersets are in constant use by all PCs, and sometimes more than one set, which isn't automatically true with all Cortex Prime systems. I'm not sure if this was also true with the other Cortex Plus games, since I didn't own any of them.

 

[Thomas Shey]

"Plus sets" are only added when they are relevant. Most Cortex Prime games have 3 prime trait sets (Distinctions plus two others) and 2-3 "plus sets". All applicable signature assets, created assets, and complications can be added to a pool. Because of this I very rarely see pools of only three dice. While it's not typical, I've seen 8, 9, and even 10 dice in a Cortex Prime pool.

Yeah, in the LOGAS game I ran for a while, I want to say I almost never saw less than 5 dice in play from the player side.

 

[Aldarc]

Yeah, in the LOGAS game I ran for a while, I want to say I almost never saw less than 5 dice in play from the player side.

More chances for hitches.

 

[Staffan]

One thing to note...distinctions are a prime trait set and are assumed (and highly recommended) for all Cortex games. A distinction will be included in every roll. If for some reason a distinction doesn't quite fit the fiction, hinder one of them instead. If it often occurs that no distinction is really fitting for what the character is doing, you have a problem. Either the distinctions are out of tune with the game's situations, or the game's situations are out of tune with how the characters were built. You need to change one or both. It's also super important to remember that the player decides when to hinder a distinction. They don't have to justify it. They just roll a d4 instead of a d8 and get a plot point.

Hmm. My impression was that distinctions are a thing you will often, but not always, add to a roll.

Even so, let's say you're rolling three dice, e.g. d6+d8+d10. That gives you a little over 1/3 chance of rolling at least one 1, which means you only have two dice left and none for Effect.

 

[timbannock]

Hmm. My impression was that distinctions are a thing you will often, but not always, add to a roll.

Even so, let's say you're rolling three dice, e.g. d6+d8+d10. That gives you a little over 1/3 chance of rolling at least one 1, which means you only have two dice left and none for Effect.

I'm not a math guy, but here's a wonderful discussion of dice probabilities with the math done out.

As for distinctions, here's the text straight from the Cortex Prime Game Handbook:

Distinctions are one of the main ways to earn PP. Every Cortex Prime game should include distinctions as one of the prime sets, which means your distinctions should be varied and broad enough that one of them will apply almost every time you put together a dice pool.

As with every Cortex rule, assume there will always be exceptions: Distinctions are not required to play a Cortex game. But they are assumed to be present by default, and when they are, they are assumed to be one of the Prime Sets and also have the Hinder SFX.

I take it as "Distinctions should be present on the vast majority of dice rolls, if not all." And there should be a really good reason why you're not including it, since it can be either positive or hindered. YMMV

 

[RivetGeekWil]

Hmm. My impression was that distinctions are a thing you will often, but not always, add to a roll.

Even so, let's say you're rolling three dice, e.g. d6+d8+d10. That gives you a little over 1/3 chance of rolling at least one 1, which means you only have two dice left and none for Effect.

@timbannock summed it up nicely, but my take is that prime traits should apply 99.99% of the time to all rolls. If that isn't happening, there's something not tuned correctly with the traits, themes, or situations of the game. If you have relationships as a prime trait and some non-zero portion of your rolls relates to things that couldn't come down to how important a relationship is to the PC, you have a problem.

I take a decided minority approach that a distinction doesn't have to apply to a situation in a fine-grained manner. I also think that players are responsible for deciding if a trait applies to the roll they are making. Those two things combined mean to me that if a player does not think any of their distinctions apply, they can just hinder one of them. You can hinder a distinction even if it could be applied positively. They don't need a justification. If one of your distinctions is Suave Smooth Talker, you could just say, "You know what, I'm having a really bad day today, so I'm a little rude to them", roll a d4, and take a PP. This is part of encouraging players not always to have their characters make perfect decisions in every situation and having a core principle of player agency in a game. Cortex works better for me when I facilitate that.

 

[pemerton]

@timbannock summed it up nicely, but my take is that prime traits should apply 99.99% of the time to all rolls. If that isn't happening, there's something not tuned correctly with the traits, themes, or situations of the game. If you have relationships as a prime trait and some non-zero portion of your rolls relates to things that couldn't come down to how important a relationship is to the PC, you have a problem.

I take a decided minority approach that a distinction doesn't have to apply to a situation in a fine-grained manner. I also think that players are responsible for deciding if a trait applies to the roll they are making.

In all the MHRP and Cortex+ Heroic that I've GMed, I don't think a pool has ever been put together without a distinction on the player side, or for a NPC; and even when rolling the Doom Pool I almost always include a Scene Distinction. I agre with you that these are the core colour and thematics of play.

let's say you're rolling three dice, e.g. d6+d8+d10. That gives you a little over 1/3 chance of rolling at least one 1, which means you only have two dice left and none for Effect.

The chance of avoiding a 1 with that pool is 5/6 * 7/8 * 9/10, = 315/480. So yes, a 165/480 (= approx 1/3) chance of a 1. At least in MHRP, that means the Effect defaults to either d4 or d6, depending on exactly what category of effect is intended.

In MHRP and Cortex+ Heroic, the main time I see pools that small is in social situations, where power sets are less likely to apply and so you might have just Distinction, Affiliation and one die from a Specialty or an Asset or similar.

 

[aramis erak]

That's part of the key; MH assumes powersets are in constant use by all PCs, and sometimes more than one set, which isn't automatically true with all Cortex Prime systems. I'm not sure if this was also true with the other Cortex Plus games, since I didn't own any of them.

It's not.
Powersets don't even have direct comparisons in Leverage... Nor firefly.
Leverage is core roll of Attribute + Role + distinction. Optional gear and conditions.

Firefly has default assumption of Attribute + Skill + Distinction, with specialization adding a d6. Distinctions also carry the FX.

Marvel has distinctions, Affiliation, one to 3 powersets (with one or more powers each and often several FX), Specializations (aka skills), and often assets; up to 3 damage track complications, and no limit on other created complications/assets. But when rolling: 1 distinction, 1 affiliation, one power per powerset, one specialization, one asset, one target complication; each plot point spent allows adding another from any of those groups except affiliation. So, you don't normally get more than 4-6 dice; one can, however, wind up with pools into the 8-10 range, not counting the mob rules nor the giant critter rules.

FX refers to mechanical special rules...
In Firefly, they're attached to Distinctions. (And so are starting skills.)
In MHRP, they're attached to Power Sets.
Various effects do interesting things, such as "step down then double" a particular die - so that d10 Flight becomes 2d8, for example - or "spend a Plot Point to pick a second damage die for another target." Or even "Step up your ___ power for this action, then shut it down for the rest of the session."

It's also worth noting that Firefly lacks a doom pool. NPCs have stats and skills, and difficulties default to either opposed by NPC or opposed by 2dX (X varies by difficulty). ISTR that the doom pool is (in published Plus designs) unique to MHRP.