Advice on a game mechanic

[jgsugden]

I am building a game and am settling in on the mechanic for how you determine if you succeed at something or not. I thought I'd share the idea here and ask people for their comments on the idea.

This mechanic would be used when you want to determine if someone was able to achieve a task, whether that is connecting on an attack, determining if they know something, or trying to be sneaky.

You would determine your result by rolling one or more dice. The size and number of your ice would be determined by your character abilities and the circumstances.

Attribute Dice: Each role would tie to an attribute, and each PC would have a die assigned to each attribute. Some PCs might be strong PCs and have d10s associated with the Strength. Others might be weak and have a d4 associated with Strength.

Skill Dice: Some rolls would also benefit from skilled training you have. This would result in a you being able to roll a second die. The size of the die would be determined by your training, as opposed to the attribute die which reflects your natural ability.

Circumstance Dice: The third (and potentially fourth) die would be circumstance dice the DM might add to your roll based upon factors that give you help in achieving your goal. This might be the help of an ally, favorable environmental conditions, or other impacts. There would be a system for assisting the DM with identifying these circumstance dice, but the rules are beyond the scope of this post.

Exploding Dice: Every time you roll a die, if you get the maximum value, you reroll the die and add a number to the result that is one less than the maximum value on the dice. If you roll the maximum value for the dice again, you reroll and add one less than the maximum on two dice. A third maximum value would get you a third reroll and adding one less than the maximum of three dice.

Your check result would be the highest roll amongst your attribute, skill and circumstance dice.

All die rolls would have a critical failure, failure, success and critical success thresholds.

Example: Nick the Knight is strong and skilled with the sword. He and an ally are attacking a monster. His Strength Attribute is d8, his swordsmanship skill is d10, and because he is working with an ally he gets a circumstance die of d8. To determine his success, he would roll a 2d8 and 1d10. If the results were 1 and 8 on the 8 sided dice, and 9 on the 10 sided die, Nick would reroll one of the d8s (the 8) and add 7 to the result. If it were a 1, his results for his dice would be (7+1=) 8, 1, 9 - so his check result would be a 9. If the reroll was a 5, the dice results would be (7+5=) 12, 1, 9 - so his check result would be the 12. We would compare that to the defense ability the monster was using to determine whether they had a critical failure, failure, success or critical success.

The more dice you roll, the less likely that you'll get a critical failure - but one would always be possible. You can roll four 1s, even on 4d20 (although it would be rare). Further, any roll could be a high result, but your odds of a higher result increase by rolling more, and larger dice.

Questions:

Do you understand the idea?

Does it seem interesting?

Does it seem too fiddly?

Does the exploding dice mechanic interest you?

 

[Jd Smith1]

You just described the resolution process of Zweihander RPG.

 

[pemerton]

Versions of this systems are used in a quite a few RPGs. Ones I know include Cthulhu Dark, Marvel Heroic RP/Cortex+ Heroic (in this case the player adds two of their dice to get their total) and Agon (the GM gets only the best die, but adds a fixed number to it; players get to add two dice). I think BitD also uses a version of this.

The exploding dice mechanic seems harmless enough but perhaps not that significant - eg if the highest typical die is d10 then presumably difficulties above 10 aren't that common, and having a d8 have a one-in-8 chance to become a d8+7 doesn't seem to change the odds all that much.

Another thing to look out for with exploding dice is the effect they have on progression. Prince Valiant has a different version of this issue: if all the dice in your pool come up successes, then you get a bonus success. So a one-die pool gives either no successes (the single die rolls 3 or less) or two successes (the single die rolls 4 or more, and because every die in the pool succeeded a bonus success is earned). This means that while the mean number of successes on two dice is greater than on one die (1.25 rather than 1) the chance of succeeding vs an obstacle 2 challenge is greater when rolling one die (one in two) than when rolling two dice (one in four - ie two succeses on two dice, which actually counts as three successes because every die in the pool succeeds).

Most of the time this is a harmless feature of the system, and sometimes players like the fact that a low pool can succeed against a slightly higher obstacle if the rolls are lucky (the chance for success against obstacle 4 rolling 3 dice is 1-in-8, which is not utterly hopeless). But sometimes it goes from being quirk to being a bit frustrating, as in the rolling-a-very-low-pool-vs-obstacle-2 case.

I don't think your exploding dice create this sort of quirk - eg the chance to get 6, 8 or 10 with a d6, d8 or d10 is 1-in-6, 1-in-8 or 1-in-10 respectively; whereas the chance to get that result with the next lower die is (for 6 with a d4) 1-in-4 (to roll a 4, gives a 3 + the next roll) x 1-in-2 (to roll 3+ on the next roll) = 1-in-8, (for 8 with a d6) 1-in-6 (to roll a 6, gives a 5 + the next roll) x 2-in-3 (to roll 3+ on the next roll) = 1-in-9, or (for 10 with a d8) 1-in-8 (to roll a 8, gives a 7 + the next roll) x 3-in-4 (to roll 3+ on the next roll) = 3-in-32 which is still a bit less than 1-in-10. But you might want to double check my maths and just look out for any other odd possibilities.

Other than that, I'd be inclined to drop Skill + Attribute and instead move towards descriptors of various sorts: I think they're more interesting to build this sort of pool out of (eg Cthulhu Dark has 1 die in the pool if its humanly possible, 1 die in the pool if it relates to your profession (which is a free descriptor chosen as part of PC build) and a third die if you risk your sanity in making the attempt - this third die then feeds into the system's insanity mechanic).

But maybe you're already committed to attribute + skill PC building?

 

[clearstream]

I am building a game and am settling in on the mechanic for how you determine if you succeed at something or not. I thought I'd share the idea here and ask people for their comments on the idea.

This mechanic would be used when you want to determine if someone was able to achieve a task, whether that is connecting on an attack, determining if they know something, or trying to be sneaky.

You would determine your result by rolling one or more dice. The size and number of your ice would be determined by your character abilities and the circumstances.

Attribute Dice: Each role would tie to an attribute, and each PC would have a die assigned to each attribute. Some PCs might be strong PCs and have d10s associated with the Strength. Others might be weak and have a d4 associated with Strength.

Skill Dice: Some rolls would also benefit from skilled training you have. This would result in a you being able to roll a second die. The size of the die would be determined by your training, as opposed to the attribute die which reflects your natural ability.

Circumstance Dice: The third (and potentially fourth) die would be circumstance dice the DM might add to your roll based upon factors that give you help in achieving your goal. This might be the help of an ally, favorable environmental conditions, or other impacts. There would be a system for assisting the DM with identifying these circumstance dice, but the rules are beyond the scope of this post.

Exploding Dice: Every time you roll a die, if you get the maximum value, you reroll the die and add a number to the result that is one less than the maximum value on the dice. If you roll the maximum value for the dice again, you reroll and add one less than the maximum on two dice. A third maximum value would get you a third reroll and adding one less than the maximum of three dice.

Your check result would be the highest roll amongst your attribute, skill and circumstance dice.

All die rolls would have a critical failure, failure, success and critical success thresholds.

Example: Nick the Knight is strong and skilled with the sword. He and an ally are attacking a monster. His Strength Attribute is d8, his swordsmanship skill is d10, and because he is working with an ally he gets a circumstance die of d8. To determine his success, he would roll a 2d8 and 1d10. If the results were 1 and 8 on the 8 sided dice, and 9 on the 10 sided die, Nick would reroll one of the d8s (the 8) and add 7 to the result. If it were a 1, his results for his dice would be (7+1=) 8, 1, 9 - so his check result would be a 9. If the reroll was a 5, the dice results would be (7+5=) 12, 1, 9 - so his check result would be the 12. We would compare that to the defense ability the monster was using to determine whether they had a critical failure, failure, success or critical success.

The more dice you roll, the less likely that you'll get a critical failure - but one would always be possible. You can roll four 1s, even on 4d20 (although it would be rare). Further, any roll could be a high result, but your odds of a higher result increase by rolling more, and larger dice.

Questions:

Do you understand the idea?

Yes, it melds roll-and-keep methods with DC methods. You might also look at karma in ED for the idea of extra dice bought with XP. ED has a different way of reading the dice, but it does use mixed dice, which at the time was novel. The new L5R mechanics, too.

Does it seem interesting?

Does it seem too fiddly?

The most common problem identified with roll-and-keep methods is that it is hard for players to at-a-glance understand their odds. BW for example includes a table to help DMs know what they are doing when they set targets. I think your method has this same problem.

For me the benefit of roll-and-keep is just how nice it feels in play. It's tactile, and you can produce some interesting nuance in what dice are on offer and how you form them into pools. And on the other hand, the benefit of DC is it's easy for players to understand. Your method takes a shot at being best-of-both-worlds, albeit risks producing a worst-of-both-worlds feel in play. It'll be vital to playtest it early with real players.

Does the exploding dice mechanic interest you?

For me it distracts from what you might achieve. I can acknowledge the nuance of adding N-1, but then it just means I might get N anyway. My intuition is that it will be deflating to do the work of re-rolling only to get the same number. It would be better to playtest the system without, and bring it back in if it feels justified.

One thought though, would be to have only certain dice able to explode. So players will feel excited to get access to those special dice. Don't use N-1+roll though, start with N+roll. It's less fiddly, and nearly certain to be more satisfying.

 

[Puddles]

My initial reaction is the exploding dice is at odds with the scaling of dice. If the strongest fighter has a d20 and the weakest a d4, the stronger fighter is going to have their dice explode 5% or the time vs the 25% of the weakest.

Even if the averages mean the weaker fighter will likely not get close to the roll of just that single d20, I don’t think that’s how it will feel at the table.

In practice, I imagine the dice exploding will be the most exciting part but it will be the fighters that are worse at something that get to experience the chaining of exploding dice on a regular basis. Chaining 3 d4s will be 1/64 vs 1/512 for a d8, 1/1000 for a d10 and 1/8000 for a d20.

 

[GMMichael]

This mechanic would be used when you want to determine if someone was able to achieve a task, whether that is connecting on an attack, determining if they know something, or trying to be sneaky. . .

Knowing something isn't a task - or at least it's one that is very different from the other two examples. Who determines the task, and who decides when a check is needed?

All die rolls would have a critical failure, failure, success and critical success thresholds. . .

Who determines what these mean? Taking tests in school would have been rough if the four possible grades were A+, C, F, and F-.

The more dice you roll, the less likely that you'll get a critical failure - but one would always be possible. . .

Why is critical fail always possible? I tend to avoid activities in which catastrophies can happen.

Questions:

Do you understand the idea?

Does it seem interesting?

Does it seem too fiddly?

Does the exploding dice mechanic interest you?

Yes, yes, no, and no. The last is because I don't want to add maxes, subtract one, and add another roll just to figure out one result.