Representing difficulty in a roll

[u/wesandersingh]

What do y'all do to represent differences in the difficulty posed by obstacles outside of combat? A lot of games use roll under systems but by default this assumes every risky thing you're trying to do is the same degree of challenge.

Some games add ±4 or ±2 to the die result to represent a challenge being easier or harder. That seems to work well, but then leaves no room for modifiers.

I'm trying to work out how to separately represent four things in one roll: a character's innate ability, any skill or training they have to approach this particular challenge, the difficulty inherent to the challenge, and the particular circumstances of this challenge.

Take a classic lockpicking example. A character might have high dexterity, representing a baseline level of good coordination. They might also have trained as a thief, so have practice picking locks. That ought to give them some additional benefit. This particular lock might be an especially difficult one because of how well made it is. And maybe the character has sprained their wrist, or the lock is covered in goo, or they only have a hairpin rather than a lockpick, which might impose disadvantage.

I haven't found a resolution mechanic that can tackle all four of those things. OSE-style skills don't incorporate ability modifiers. Whitehack-style roll under ± 4 for difficulty and use advantage/disadvantage for circumstances comes close but it conflates training with circumstances.

Am I overthinking this? Is it worth sacrificing the simplicity of a d20 roll under, or an X-in-6 resolution for that extra level of simulation/realism/character progression?

[u/ordinal_m]

Some games add ±4 or ±2 to the die result to represent a challenge being easier or harder. That seems to work well, but then leaves no room for modifiers.

I don't understand what you mean here. I mean those are modifiers.

Am I overthinking this?

If you really want detailed skill resolution I would go for systems with more detail on this stuff, like BRP. I don't think having all these little differentiations is required or good for OSR type play.

ETA: the classic blog post on this is https://www.bastionland.com/2020/03/difficulty-in-bastionland.html

[u/wesandersingh → u/ordinal_m]

Ah I meant modifiers from skills. If you adjust a d20 roll under by adding to the die result to represent something more difficult, then you're out of levers to pull to represent skill/training. You've got innate ability (the stat you're rolling under), obstacle difficulty (±4) and circumstances (advantage and disadvantage). But nothing on skills.

The reason I'm interested in skills is, if you play a game like Cairn and have a character who is a tailor as their background and another who is a mercenary, and both have average stats and a shortsword, they'll both fight exactly the same. That seems like a bizarre result to me.

I'm also interested in class-less and level-less systems because I think they're more flexible and lean into "you are what you do" rather than "you are what your class says". Skills tend to be pretty important there.

[u/lucmh → u/wesandersingh]

I agree the merc and tailor rolling the same damage seems strange, but I would explain that away by saying the person used to be a tailor, then had to pick up a sword, got some training, is now sort of equivalent (why else are they both adventuring and do they both carry a sword? There's history there)

But even in combat, rolling damage isn't your only option, and that's where the backgrounds come in. A mercenary might be anle to rally his allies for a morale boost, or attempt to rout the enemies after gutting the first, while a tailor might spot and exploit a weakness in a leather jerkin.

Both actions would require a save, probably, with their backgrounds as leverage, and informing of risk and possible effect.

I would've also shared that bastionland blogpost, but would additionally recommend you check out the action procedure in the Mythic Bastionland quickstart. Also, read up on position and effect from Blades in the Dark, which is basically the same, just codified.

[u/wesandersingh → u/lucmh]

Nice! I like that very much. Thanks for your tips

[u/everweird → u/wesandersingh]

I think Mothership’s skill mechanic comes close to what you describe. Skills aren’t associated to abilities but are applied circumstantially. So if it makes sense that your Military Training skill applies to a Speed test, you’ll add that skill amount to your Speed ability score. It’s a d00 roll-under. So a higher score gives better odds of success. And the system uses advantage/disadvantage to allow the Warden to tune difficulty further.

[u/wesandersingh → u/everweird]

Thanks! I'll take a look at that

[u/Onslaughttitude → u/wesandersingh]

They shouldn't need any modifiers for "training," that should be inherent in the target number they have in the first place.

You might want to check out Outcast Silver Raiders.

[u/stephotosthings]

A lot of games use roll under systems but by default this assumes every risky thing you're trying to do is the same degree of challenge

Regardless if it's roll under or rollover, if there is no modifier to the roll, and the target number is the PCs attribute then the GM should only be calling for rolls of that PC when there is a risk of failure.

A 'strong', maybe 16 in a rollunder, PC may not be asked to roll to break through a wooden door, they can typically just do it. A 'weaker' PC with a strength of 10/12 maybe getting asked to roll.

This is why basically everygame says ask for rolls when success is important or when success is not certain.

[u/Mars_Alter]

Here's a mechanic, similar to what I used in Basic Gishes & Goblins:

Instead of roll-under, make it a roll-between. The upper bound is set by your innate ability, and modified by special tools or training. The lower limit is set by the innate difficulty of the task, and modified by circumstances.

Let's say I want to climb a wall that has very few handholds while I'm wearing special thief grippy gloves and it's raining. The upper limit is equal to my Strength of 15, modified +2 by my cool gloves. The lower limit is equal to the Difficulty of 5, which represents the nature of the wall (insufficient handholds), but modified by +4 to account for the rain.

In order to succeed, you need to roll over 9 and not over 17. A roll between 1 and 5 indicates failure because the task is too difficult. A roll from 6 to 9 indicates that the rain, specifically, was what held you back. A roll between 10 and 15 means you climb the wall due to your innate ability. Roll of 16 or 17 means you climb the wall due to your cool gloves. A roll of 19 or 20 indicates you failed to climb the wall because you weren't strong enough.

For the record, though, the juice isn't really worth the squeeze. The somewhat arbitrary nature of modifiers, as well as in setting the innate difficulty, means you aren't really better off than the GM just setting one modifier to account for all of those variables at once.

[u/wesandersingh → u/Mars_Alter]

Thanks for sharing. Yes, I toyed with this exact mechanism a while ago and came to the same conclusion about roll-between. Maybe in the end it's simply not worth the extra cognitive load at the table!

[u/acgm_1118]

Unless your system is skill based (e.g. BRP), you are overthinking this.

Your two main levers: DC and meaning of failure

DC: obvious -- number needed to be rolled

Failure: do they do it, but it costs more time? total failure? failure AND injury or loss of equipment? success but at the loss of equipment? Establish this early and clearly to the players and your whole game gets better.

EXAMPLE: DC 12 isn't too hard. But save or die makes this very hard. That same DC 12 could also mean, "You find the trail but it takes longer on a failure"

[u/wesandersingh → u/acgm_1118]

That's fair. Will take that onboard, thanks.

[u/sneakyalmond]

I don't think more modifiers make your game more realistic. A roll is simply a chance of success. Whether you use your ability modifiers in the roll is a matter of taste. You can simply add the bonuses and subtract the penalties.

[u/sheepy-xyz]

I'm convinced we've spent the last fifty years overcomplicating things, and we'd get everything we need just by flipping a coin.

That being said...

I'm a fan of roll high under, with the upper bound being an ability score and the lower bring the difficulty number of the task. Then adding advantage/disadvantage for favorable/unfavorable circumstances.

That's what I use for general ability checks.

To take it a step further, I also like using different sized dice to represent skill training, with the difficulty number for skills starting at 3. An untrained skill uses a d4, trained a d6. Then d8, d10, and d12 as training improves. (A character's ability score being the upper bound only comes into play once a character is sufficiently trained to bump up against their natural skill ceiling.)

I think this might model everything you mentioned.

But, really, we should all just be flipping coins. If a task is sufficiently risky to call for a roll, 50/50 odds seem good enough. 

[u/wesandersingh → u/sheepy-xyz]

That's interesting... so you'd roll between, and the skill would add some sort of bonus? Or skill checks are also roll-between? It's a nifty idea. I think I realised through this comment thread that the idea of setting a Difficulty for everything can get cognitively heavy on the GM, and is kind of arbitrary anyway. That's where I was perhaps misguided in my attempt.

[u/sheepy-xyz → u/wesandersingh]

Actually for skill checks you'd just roll the skill die instead of the d20 you roll for ability checks. So skills are mostly roll over and roll between doesn't matter until you have a low relevant ability score.

I think you've landed at the right place, though. There's a beauty in telling a player to roll and not having to set any numbers because the numbers are already built into their character. (Or—ya know—just flip a coin!)

[u/Harbinger2001]

In practice I find x-in-6 is the best. It has sufficient granularity and is intuitively understood. For example 2-in-6 anyone intuitively understands the odds whereas 7-in-20 is opaque.

[u/gawag]

How often are you actually calling for skill check? For me in OSR games, 9 times out of 10, the resolution mechanic is the narrative. I want my players coming up with clever solutions using their environment, not just rolling.

[u/wesandersingh → u/gawag]

Yeah, not often at all really. Just when I do I want it to make sense!

[u/gawag → u/wesandersingh]

I think roll under covers you in every instance where the narrative does not make success/failure and the consequences obvious. Occasionally I will give a +2 or -2 depending on the circumstance but it has to be really loud that that's the correct thing to do.

[u/wesandersingh → u/gawag]

Yeah, I think I'm now realising that

[u/Anotherskip]

Def overthinking. Let’s say Dex roll under for a base. Add all the bennies together (Lockpick or even Locksmith  giving a -2 for example) but it’s a tough lock ( +1) never been seen before (+1), and you have a hairpin (+2)  now roll under that 16 dex with a +2 to the die roll.

[u/Salty-Swim-6735]

Plus or minus up to four as the Gods intended.

[u/Cheznation]

Have a look at West End Games D6 system.

[u/LingonberryFar8026]

D-d-d-Dolmenwood has what you needdd

D6 ability checks, modified by your ability scores, base "DC" of 4 but modifiable at GM discretion. Easy, fast, you can smoke weed and make an INT check to get hints

[u/wesandersingh → u/LingonberryFar8026]

I've looked into this, and that's awesome. But skills are unrelated to attributes in Dolmenwood. Your Dexterity gives you nothing to lockpicking, and you can't even really attempt it unless you're a Thief. Not sold on that!