Core mechanic: a painfully thorough examination of every part of the 3d6

(Originally posted on Cohost: https://cohost.org/binary/post/162256-total-effect-core-m )

So this is my first public post/design blog/etc about a system I’m developing as a SRD/toolkit, Total//Effect. It includes a bunch of probability stuff at the end if you’re into that, but I do sum up the important bits if you’re not.

I’ll start with my initial forays into the humble 3d6 (and the originator of some of these mechanics), 36th Way and LUMEN.

3d6 and 36th Way/LUMEN

Total//Effect’s resolution is a kind of combination of two different resolution systems I’ve used in the past: 36th Way and LUMEN.

My first big intro to using 3d6 as a resolution method came from my own 36th Way (which is a total conversion of 13th Age). I was using it as a stand-in for the d20 there, with a pretty typical roll + bonus vs difficulty system, but also using the “Natural” value (the die roll total) like 13th Age did: 9+/11+/13+ on 3d6 maps to the same 75%/50%/25% as 6+/11+/16+ on a d20. Instead of additive bonuses/penalties, I instituted a 5Eish advantage/disadvantage: roll X extra d6’s, take the highest/lowest 3. (See my post about it here if you want more info.) This worked pretty well for that game but the D&Dishness of the general resolution dragged on me a bit (scroll down to “What am I not a fan of?” for more on that). This is especially true of Natural vs. total: more than a few players had a sticking point with this in particular. Players don’t want to hear that their natural roll was a 14 (relevant points to their ability: natural 13+, natural even) when they clearly rolled a 21 after adding stuff. And honestly, who can blame them? I get why it’s there but it’s definitely a “train yourself to be used to this” kind of thing.

My second came indirectly from LUMEN. LUMEN uses a FitD-style “roll Xd6, take the highest” situation, with 2-3 dice being fairly common. 3 is the maximum I set for Attributes for APOCALYPSE FRAME because LUMEN splits its bands into 1-2 fail, 3-4 mixed success, 5-6 success: with that split, 3 dice ends up being 5% of a 1-2, 25% of a 3-4, 70% of a 5-6. (More on this here.) I like this a lot and it’s probably one of the faster resolution systems I’ve seen! LUMEN, however, has to use fixed Harm/etc values to avoid slowing things down with multiple rolls, which I think is great for a certain kind of game about knowing exactly what you’re capable of but isn’t like wildly flexible.

Finally, I got the idea of using 1 die at a time from an old prototype of a game I wrote like 7 years ago that didn’t go anywhere because it was way too involved. (No link to this one because this was like the one good idea in there - it was using the individual dice from Initiative rolls to determine energy regeneration based on general type of character. There was a lot going on in that game.)

The Mechanic: add dice for Total, pick dice for Effect

Total//Effect is named that because you’re looking for up to two different things in each 3d6 roll:

• The Total, aka the sum of 3d6
• The Effect, aka a specific die (Low, Mid, High) from those 3 dice rolled.

In general to use the Total, you’re rolling against values set by the ability itself, or for generic cases:

• 8-: PC’s choice: either the attempt fails with a minor consequence/twist or the attempt succeeds with a major consequence/twist.
• 9-12: The attempt succeeds with a minor consequence/twist.
• 13+: The attempt succeeds without consequence.

(X+ meaning that value or higher, X- meaning that value or lower, X-Y meaning between X and Y inclusive.)

The Effect is defined prior to rolling in the case that there’s a numerical component to success, usually in the form of one die that’s being used. (For example, if you’re rolling to gather supplies, the GM might say that on a success you gain Mid Die supplies.) You can then use character qualities as appropriate (skills, equipment, etc.) to give Advantage to the roll (roll 1 extra die, highest 3) or increase the die used for Effect. You can also use one or the other in a given situation. To provide a more specific case as an example, here’s a (stripped down to the rolling bits) combat ability:

Defensive Jab: Low Die Harm.

9+: Reduce the next instance of incoming Harm by Low Die.
13+: Mid instead of Low Die for both.

Which is to say: by default (on a Total of 8 or less) it does Low Die Harm, on a 9-12 it does that but also reduces the next instance of incoming Harm by Low Die, and on a 13+ both effects are present and use the Mid Die instead. It’s pretty low-Harm (usually 1-2) unless you roll very well…or unless you’re gaining Advantage, or unless escalation is high enough that you’re hitting that 13+ fairly often. (More on how often that is later.)

On top of this, you have Escalation (stolen lovingly from 13A/36W). Unlike in those, Escalation is the only additive property in the game: it adds to or subtracts from a roll’s Total based on increasing tension or some similar property in a situation (for example, it might add to combat-related rolls but takes away from rolls to do more collected, rational things). It can also add to or replace Effect for certain abilities (like certain combat abilities might add Escalation to Harm/Damage/etc).

Permutations

In addition to the above, I’ve also come up with a few other slight tweaks on the mechanic:

• Rolling against PCs to see the details of a consequence on a roll. For example, rolling to see how many hours something takes upon provoking a consequence, using a higher die for a more major consequence. Similar to how they can add Advantage/increase the die used for rolls they make, PCs can use character qualities to mitigate these through Disadvantage/using a lower die - but they can’t use the same thing twice on a roll/counter-roll combo, so there’s some strategy of using everything up-front for the best outcome vs. mitigating consequences.
• Rolling and using multiple dice. For example, negotiating payment for doing a job well might get you High Die payment for doing it perfectly, Mid Die for doing it adequately, Low Die for doing it poorly. Another example might be an ability that uses one die for number of targets and another for the actual effects.
• Roll, pick a die based on the situation, then see if it’s higher/lower/equal to a value rated 1-6. For example, Relationships are measured by a number of Bonds: when you want to influence the other party to do something, you pick Low/Mid/High die based on how likely they are to do it on their own and roll, taking that die and comparing to your number of Bonds to see how well that works out.

I’ll likely come across more permutations in the future, but that’s what I’m working with right now.

Probability Details

Takeaways

• The biggest change that happens to Total for Advantage/Disadvantage is to the high values: 13+ goes from 25% to 50% on Advantage (2x as likely) or 10% on Disadvantage (2/5 as likely).
• High/Mid/Low increase by .25/.5/1 for Advantage. This means that it makes a bigger difference for Low/Mid dice on rolls. And vice versa for Disadvantage.
• Increasing/decreasing the die used (Low to Mid to High or vice versa) is a bigger change on any given die value than gaining Advantage/Disadvantage but keeping the same die, which makes picking one of those bonuses/penalties over the other an actual choice. (More complex outcomes like specific abilities can increase the die used on higher Totals as well, as shown above, but generally speaking: Advantage/Disadvantage has a greater effect on Total, while increasing the die used has a greater effect on Effect, which is largely what you should be able to expect from both of those choices.)
• As noted by the 9+/11+/13+ distinction in 36th Way upthread, adding escalation 2 means you’re hitting 13+ 50% of the time - and subtracting it means you’re hitting 9+ 50% of the time. Combined with the probabilities above, this is effectively like an extra Advantage/Disadvantage with the caveat that it’s not changing any of the die values used. So while the Total will shift, changing the terms of the roll, the Effect isn’t going to change based on this. (This also feeds nicely into my assertion that most combats should be 3 rounds: Escalation 2 hits exactly at that third round if starting at Escalation 0.)

Conclusion? Summary? Endnotes?

I’ve started sketching out and playtesting some games with it and I like what I see! You have a pretty good idea of where a roll is going to end up as far as Effect, but with a lot of room for surprises (like in one playtest I did, a low die Harm roll went sideways when I rolled triple 6’s.) It’s fast and feels pretty good!

I’ll have more long-form thoughts about this as I roll out the whole SRD/toolkit, there’s a lot more to it than one roll mechanic. But these are my thoughts going into it. Hope it was helpful or enlightening for you!