I've been working on this core mechanic for some time, and I think I need a few opinions from someone who hasn't been working with it to answer some really basic questions. This core mechanic is intended for an aggressively experimental strategy-horror RPG, and is intended to provide experienced players with power-user features.

The Composite Pool

Your skills and attributes are measured in die sizes, with D4 being the best and D20 being the worst. When you attempt an action, you will fill four die slots with dice representing relevant skills and attributes and roll them. Your GM may write custom Check Splicing rules to dictate how you can fill these die slots. Generally, you need a minimum of two skill dice to use a skill, and you may not roll four dice all representing the same skill or attribute.

Count the number of dice which roll 3 or lower as a success.

A number of mechanics--such as receiving assistance or spending extra AP in combat--give you Boosts, which allows you to bank your successes and reroll some of the dice. When you add a Boost to a roll, you may choose which dice to reroll, but you should roll all your Boosts out at the same time, and may only Boost any given die once. Again, count how many dice roll 3 or lower as a success.

Generally, the GM will compare the total number of successes you rolled against a set TN: 1 success is Easy, 2 is Normal, 3 is Hard.

A Few Designer Notes

The point of this mechanic is that there is no set "right" way to assemble a composite pool, and that optimizing the pool both encourages you to think in-character and rewards you with a better chance of success. It also captures a lot of nuance; in most systems, if you want to cook an egg, you have to roll using a dedicated cooking skill. In this one, you can create different die rolls to represent different ways to cook the egg. If you're hard-boiling it, you could go with your intelligence mixed with one knowledge die, and if you're scrambling it, you could mix dexterity and strength.

The reroll round also adds an element of diminishing returns to the roll. The dice in the pool are probably not all the same size, so if you reroll the smalles (best) dice first, you wind up asking yourself if it's worth spending extra to add in the larger dice.

The advantage is that the player gets these design features while having to do essentially zero arithmetic, at least to run the core mechanic itself. There are three tradeoffs. It can cause analysis paralysis. It requires a lot of dice fishing to set the roll up. Experienced players who know how to assemble the pool in their favor have PCs who almost never fail at tasks, provided the PC is good at what he or she is doing, and the player is having the character spending a reasonable amount of effort on it.

Well, two and a half. I think it's arguable the last one is more a positive feature that most GMs are not used to than an actual drawback.

The Questions:

Is four die slots and a default TN of 2 successes the correct way to go?

The system I intend to pair this with has 4 attributes and 20 skills. This means that with 4 die slots there is a little less than 1.6 million possible pool and Boost combinations (24^4 * 5). That might be a bit much. However, if I drop the number of die slots to 3, there's a fair bit less fishing for dice, and there's still about 50,000 possible pool and Boost combinations. But then I also have to drop the base TN down to 1, so there's no longer any way for the GM to make a roll easy. There's just normal, hard, and harder.

I've been messing with both approaches for some time, and when I play the game now, I feel like the three die slot version is claustrophobic. It isn't just that the difficulty granularity decreases; as a player, I don't quite have the creative space to use two skills at once or throw in a weird die to represent doing something strange, like throwing intelligence into a gunshot to lead a moving target. The four die slot version does that just fine. But at the same time, I've been messing with this mechanic for several years, now, and I am now probably far more comfortable with it than most players and GMs will be.

I know that three step die pool systems can work because that's how Cortex works. I've never seen a successful commercial system with four mixed step dice. But at the same time, this is a zero arithmetic core mechanic. Perhaps I can get away with it? I don't know. I'd really like some feedback on this point.

Would you prefer a three die slot version with better speed and practicality, but very little granularity and less space for customizing the roll, or a four die slot which adds the complexity of another step die, but has a lot of space and somewhat better granularity?

Well you always have options:

Maybe you can only get the 4th dice in certain conditions. Bob is helping you? Add a die for Bob. You spent the prior round preparing? Add a die for that preparation.  (Sounds like you may be using these for your "boosts" but rerolls aren't as "core" as the number of dice you roll to begin with.)

The other main thing for making something easier, is changing the success threshold on the die. Instead of needing a 1-3 for a success, extend that to 1-5 etc.

Mechanics like this are best when rolls are relatively infrequent and do a lot (because of the amount of decision that goes into each roll.)

I absolutely agree this mechanic is not something a group should use constantly; I intend to supplement it with a completely diceless mechanic for simple yes/ no answers or to avoid metagame tells when doing things like passive perception.

The reason I'm not inclined to switch between one and the other like that is that the three die version needs a lower success count threshold to work. In order to prevent maximum rolls from always being the optimum solution, the first success needs to have the most effect, so that players looking to optimize their DPS are also encouraged to take a chance they will undershoot. If you lower the difficulty, then the extra successes you could get from a 4 die roll become extraneous. It becomes much harder to balance the farther you go away from the basic roll; it will either always be optimum because damage output is higher and risk is lower, or it will never be optimum because it's too far away from the first success.

I really don't like the idea of modifying the TN. This mechanic already has character-specific approaches, multiple ways for the GM to modify difficulty for fictional position, and a way to modify the roll for how much effort the PC is taking on the action. This is definitely flirting the line with being overbuilt, already, only saved by the fact that it is a zero-arithmetic dice pool. Modifying TN or adding another mechanic which lets you change the number of dice will probably push it over the edge.

Thank you for the comment. I think I will go with the 4 die version and rely heavily on the diceless alternate mechanic to make up for the added weight because that makes the unique abilities of this core mechanic more visible. I expect it's better to be visibly different and deliver on differences than it is to be streamlined, OK, and not that different from the norm.

Quote from: Fheredin on January 31, 2022, 01:55:48 PMYour skills and attributes are measured in die sizes, with D4 being the best and D20 being the worst. When you attempt an action, you will fill four die slots with dice representing relevant skills and attributes and roll them. Your GM may write custom Check Splicing rules to dictate how you can fill these die slots. Generally, you need a minimum of two skill dice to use a skill ....

Maybe use another word here that covers both attributes and skills, e.g. Abilities or Capacities. I assume that some rolls could be made without benefit of an applicable skill and others not.

QuoteCount the number of dice which roll 3 or lower as a success.

Purely as a probability note, even the best possible pool of 4d4 by this still has only about a 42% chance of success at a Hard roll, if my math is right, and assuming that the "average" die size is d10 and a stereotypical "average" pool would then be 4d10, the chance of at least 2 successes for a Normal roll is still pretty low (4d10 fails even Easy rolls 1 time in 4).  Stipulating that this is a horror game and that PCs may have to cope with lower effectiveness than they're used to, this could still wind up pretty frustrating.

QuoteA number of mechanics--such as receiving assistance or spending extra AP in combat--give you Boosts, which allows you to bank your successes and reroll some of the dice. When you add a Boost to a roll, you may choose which dice to reroll, but you should roll all your Boosts out at the same time, and may only Boost any given die once.

So you could have in effect up to 8 dice and 8 successes on a single roll, in theory, if you were willing to spend 4 Boosts for it?  How many Boosts can players generally count on being able to secure at critical moments?

QuoteIs four die slots and a default TN of 2 successes the correct way to go?

I'd keep the four dice but reduce the "default" TN to 1; as noted above, if d10 is "average" rank for a given ability (this gives you 3 ranks above average and 2 below), then a 4d10 pool will still get no successes at all about 25% of the time.  Anything that's "Easy" in a horror game should be taken as read, I think; you only roll when there's significant stress on the outcome, and difficulties of Standard, Hard and Terrifying seem like they'd fit perfectly well.

Quote from: Stephen Tannhauser on April 05, 2022, 03:18:13 PM

Quote from: Fheredin on January 31, 2022, 01:55:48 PMYour skills and attributes are measured in die sizes, with D4 being the best and D20 being the worst. When you attempt an action, you will fill four die slots with dice representing relevant skills and attributes and roll them. Your GM may write custom Check Splicing rules to dictate how you can fill these die slots. Generally, you need a minimum of two skill dice to use a skill ....

Maybe use another word here that covers both attributes and skills, e.g. Abilities or Capacities. I assume that some rolls could be made without benefit of an applicable skill and others not.

Possibly. Part of the goal here is to create a space for mixing and matching and custom rules so the game feels open to player creativity and GM customization at the core mechanic level. I like how this is a system were you can use a preset formula to cook an egg, or come up with a dozen other checks for it. That said, to bother including skills you either need to require them when they're worse than the attribute or allow the player to make them notably better than the attribute. This isn't what I'd call a clean design victory.

QuoteCount the number of dice which roll 3 or lower as a success.

Purely as a probability note, even the best possible pool of 4d4 by this still has only about a 42% chance of success at a Hard roll, if my math is right, and assuming that the "average" die size is d10 and a stereotypical "average" pool would then be 4d10, the chance of at least 2 successes for a Normal roll is still pretty low (4d10 fails even Easy rolls 1 time in 4).  Stipulating that this is a horror game and that PCs may have to cope with lower effectiveness than they're used to, this could still wind up pretty frustrating.

See note on Boosts.

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QuoteA number of mechanics--such as receiving assistance or spending extra AP in combat--give you Boosts, which allows you to bank your successes and reroll some of the dice. When you add a Boost to a roll, you may choose which dice to reroll, but you should roll all your Boosts out at the same time, and may only Boost any given die once.

So you could have in effect up to 8 dice and 8 successes on a single roll, in theory, if you were willing to spend 4 Boosts for it?  How many Boosts can players generally count on being able to secure at critical moments?

During combat? All 8. Out of combat is trickier.

The action economy I intend to attach this to is an AP system, which allows players to spend more AP to take bigger actions. The default AP cost of a rolling action is the number of die slots plus the number of boosts, so if you spend 8 AP to buy an action, you will get all 8 dice. If you spend 6 AP, you will get a full first roll, then 2 Boosts. If you take a minimum 4 AP action, you only get the first roll. The basic idea is to capture the distinction between fast and light attacks and slow and heavy ones like you see in many fighting games. Although I suppose here it's actually commitment vs probability of success.

Out of combat, Boosts represent things which are giving you an advantage, such as a character assisting you or if there's a notable fictional circumstance in your favor. I'm not a huge fan of how combat has to act as a light-switch for being able to spend AP, but AP recharges so fast out of combat that it really makes no sense. It would break the mechanic to allow AP to be used outside of combat.

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QuoteIs four die slots and a default TN of 2 successes the correct way to go?

I'd keep the four dice but reduce the "default" TN to 1; as noted above, if d10 is "average" rank for a given ability (this gives you 3 ranks above average and 2 below), then a 4d10 pool will still get no successes at all about 25% of the time.  Anything that's "Easy" in a horror game should be taken as read, I think; you only roll when there's significant stress on the outcome, and difficulties of Standard, Hard and Terrifying seem like they'd fit perfectly well.

That does sound sensible. I typically try to make difficulty a non-dice thing for horror games, meaning that I give them more to the player than to the player character. However, the GM can always increase the TN with little to zero effort.