Choose Your Own Adventure: Resolution Mechanics

 

Album Cover, Virgin records

There are a whole collection of different ways people resolve things in TTRPGs. Dice, cards, tarot, jenga blocks, dominos, points, candles... it's absurdly diverse. Since we're trying to make RPGs, it would make sense to take a look at some options before making our decisions. Me, personally? I love dice. I'm a dice goblin, my wife is a dice goblin, all our friends are dice goblins... it's going to be dice.

Originally, war games used d6s only - they've been around for thousands of years, and even now, when most people think "dice", they think of d6s. When we entered into the era of what is now considered TTRPGs, those were stepped away from relatively quickly. The first era was that of linear dice - these are dice resolution systems that emulate some amount of easily-computable percentage statistics. Dungeons & Dragons, rather famously, used the d20, where each face has a 5% chance of being rolled, and other systems such as Palladium followed suit. The other early games, such as Basic Role Playing (BRP), it's spinoffs (Call of Cthulu, Runequest, and so on) and Warhammer, used a d100 - a pair of d10s, one representing the 10s place, and the other in the 1s place, where each digit is 1%. Other dice were still being used for any number of other things

Relatively quickly, that started getting spread around. Tunnels & Trolls replaced the linear resolution method with one that contains a "bell curve" - 2d6. This got spread around even more with systems like the General Universal Role Playing System (GURPS), with their 3d6 system handling more and more nuanced systems.

These types of systems are all about comparing numbers, and fall into 3 categories: 

• Roll-Over - the rolled number is compared against a Target Number (the difficulty level) provided by the Game Master, and if it's above that number, it's a success.
• Roll-Under - Instead of receiving a number by the GM, Roll-under systems have the Target Number there on the Sheet (If my sheet says 10, for example, I need to roll and the total needs to be at or under 10). There are two of these executions - first, the modifiers effect the dice rolled, like the above, but are in a state where negative numbers are better (TN 10, I roll a 12 but have a -3 in the trait, for a total of 9); alternatively, the modifiers effect the Target Number, and thus math is done first and the dice rolled second (TN 10, I have a +3 in the trait, so the actual target number is 13) 
• Contested - One of the above systems, but instead of a static difficulty, the player's dice and total are compared to the dice and total rolled by the GM

The next innovation was that of a 'dice pool' system - where dice are rolled, certain numbers are labelled as success, others as failure, and then a number of successes are counted. First with Ghostbusters (1986), which used a d6 pool system, the largest game that used such a system was the gothic monster games in the World of Darkness storyteller system (using d10 dice pools) and the Fudge d6 system, with their custom d6 dice that contain two "+" , two blanks, and two "-" signs (which are abbreviated as "dF"). Star Wars Roleplaying 2012, later released as Genesys in 2017, took that a step further, uses "narrative dice", a custom set of polyhedral dice that are used.

Dice pools are interesting because you have multiple "levers" to twist - not only is there a number of successes that can be generated, but what defines a success can be leveraged. In some Shadowrun editions, a d6 pool system, 5s & 6s are successes, but since the number of dice can get really large, there's an alternate rule that you can just automatically gain 1 success for every 4 dice that would be rolled (outside of combat, that is). In some of the World of Darkness editions (d10 pools), typically 6-10 are successes, 2-5 are null, and 1s are failures... but in some cases that number that defines success could get higher (7-10 or 8-10, for example). 

The next innovation was the fixed Target Number, introduced through the games that would become Savage Worlds in 2003. That system used a linear resolution (a single die and modifiers), and a fixed target number (4), but also added the concept of "exploding" dice - that is, if you roll the highest number on the die (a 4on a d4, an 8 on a d8, etc), that die is noted and then rolled again. Because of this, otherwise impossible resolution calculations, such as 1d4-2 vs a TN of 4, could be accomplished. While this solved many issues that linear resolutions had, the desire for low numbers to trigger additional "explosions" often meant resolutions make take quite a while - roll, and then roll again, and then roll again.

In 2010, Apocalypse World  took the RPG space by storm, eventually spawning hundreds of "Powered By The Apocalypse" games in its wake. They main innovation of the PbtA-style systems is that they took that fixed difficulty model, and used it to mirror both sides of the interaction - using a 2d6+ roll-over system (originally), the player would roll their dice, add a modifier and compare it against a chart:

• 1-6: Failure, and the GM makes a move
• 7-9: Partial Success (or Success, with complications), with the GM having a relatively fixed number of options for that complication
• 10+: Total Success

This shifted the balance away to an entire liminal setup - the GM doesn't roll at all, just presents a threat, the players act, and the GM reacts. There are also variants of this with other dice sizes (such as Monsterhearts & Kult which use 2d10). In 2013, this concept was ported over to d20 systems with Numenera, which eventually became the Cypher System, attempting to be a combination of both worlds.

An off-shoot of the PbtA craze was the game Blades in the Dark, which uses a combination of dice pools and the above system - Referred to as "Roll and Keep". With this setup, there is no (or very little) math involved. In this setup, you create a pool of d6s, and use only the highest result. 1-3 is a failure, 4-5 is a partial success, and a 6 is a total success (multiple 6s is considered a critical success). In TechNoir, a d6 pool system, 4-6 is a success and 1-3 is a null, but "Hurt Dice" can be added which remove the numbers rolled from the pool (so if you have 3 successes with a 5, 5, and 4, but one of your Hurt dice rolls a 5, those are negated, and you're down to a single success). The various Cortex systems are similar, where you roll a number of dice (but of various sizes), and you "keep" two of the dice for your total. In 2022, the concept was iterated on again, with the Breathless system - No modifiers, only dice sizes, and each time you roll a die, you keep the next smallest die. 1-2 is a failure, 3-4 is a partial success, and 5+ is a full success. This combination allows for the Stakes to constantly stay high, as each time a check is needed, whatever die that check is using will step down the die - It's really easy to roll over a 5 with a d12, but then it's a d10, then a d8. The lowest die that can be used is a d4, which means the checks can still succeed, but always at a cost. 

So, with all that out on the table, what do I want to actually use?

One of my largest gripes about RPGs in general is that difficulty is abstract, and the system revolves around having a Target Number. In some cases it's really straightforward - if you're fighting a creature, that creature typically has some sort of stats, and then the Target Number is derived from that. In D&D, it's numbers like the Armor Class (AC) or Saving Throws. In Cypher, it's the difficulty level multiplied by 3 (A level 4 creature has a TN 12). But outside of those predefined things, that abstraction is even more made-up - If you're falling and want to grab a ledge, how hard is that? If you have peak human strength, and want to lift a car up, how difficult is that for you? If you're trying to jump between moving carriages, what is the Target Number?

For that, the Roll-Over systems are largely devoid of value. There's always a table of some variety, some collection of "easy" to "hard" to "nearly impossible" with some numbers, but they're always devoid of context, and have no background information on how to make that work. The only Roll-Over system that works well is the PbtA model of game, where there is a constant Target Number. Roll-Under System seem to be the way to go for that specific complaint.

As a game master, I tend to be tracking a lot of things - while each player has a lone character, maybe a second one, the GM is tracking everything and everyone else. I like mass conflicts, I like things that are complicated and interesting. Because of that, I want enough of an abstraction where I'm not constantly having to track every little thing. That being said, I also don't want to go too deep into the realm of PbtA, BitD and Cypher - I still want to be rolling dice, and playing the game, just on a more reduced scale.

Instructions Unclear, Roll-Under seems hard

Roll-under seems like the way to go - having the bulk of the difficulties right there on the page would make things run really fast for the most part. Definitely the version where all of the math is done on the front end, though, manipulating the target number instead of the roll itself. That being said, many of the roll-under systems are linear instead of bell-curve, so that's a problem. Ironsworn (a solo-focused 2d10 system) and the Modiphius 2d20 systems (for games like Mothership, Conan, Fallout or Dune) are the only ones I know of. More research will be required.

I particularly like the degrees of success that is used in Hollows, a d20 roll-under, as the presence of enemies is represented as adding a second, lower Target Number, and the ideal roll is going to be at or under your TN but above the enemies'  TN. Gotta thread that needle really smoothly. That being said, I also enjoy that lower-equals-better from Modiphius, though - where rolling double 1s is an amazing roll. 

However, if there's a particularly asymmetrical version of contested rolls out there, that might also be interesting. Ironsworn, mentioned above, has a somewhat-contested roll, in that the Target number is determined by the Stat on the sheet added to a 6d. The Cortex dice-pool system, such as in Tales of Xadia, has difficulty levels are based first on dice pairs, but the contested pools are augmented by things like location distinctions and the character's own complications. For example, Recovery is against the base difficulty of 2d8 - so if you're bleeding d10, you would roll against the combined two highest numbers from 2d8+1d10. That also some serious potential.