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Inverted BRP?


Darkholme

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Hi Guys; new to the forums, new to BRP, but not new to RPGs, or to the d100 roll under concept (though my experience with it is through warhammer RPGs).

I really like alot of the BRP Stuff I've been reading; but I'm not a big fan of the roll under mechanic. I think it works great for opposed tasks, but works less well for static tasks. I dislike that you're essentially rolling against your own skill, instead of rolling against the difficulty of the task.

How hard would it be to invert the rolling system, so you're still rolling d100, and still using the same modifiers, but instead of trying to roll under your skill, you do some kind of d100+skill vs target numbers; Something akin to the Target Numbers in Rolemaster or D&D, or something similar but a bit more simple like degrees of success in Unisystem?

~DH

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Hi Guys; new to the forums, new to BRP, but not new to RPGs, or to the d100 roll under concept (though my experience with it is through warhammer RPGs).

I really like alot of the BRP Stuff I've been reading; but I'm not a big fan of the roll under mechanic. I think it works great for opposed tasks, but works less well for static tasks. I dislike that you're essentially rolling against your own skill, instead of rolling against the difficulty of the task.

How hard would it be to invert the rolling system, so you're still rolling d100, and still using the same modifiers, but instead of trying to roll under your skill, you do some kind of d100+skill vs target numbers; Something akin to the Target Numbers in Rolemaster or D&D, or something similar but a bit more simple like degrees of success in Unisystem?

~DH

I'm not aware of any rules that allow you to do that, but there is the Blackjack mechanic, which is presented as an option in the BGB. Using this, the goal is not to roll low, but as close to your skill ranking as possible. Thus, if you have a skill of 69%, rolling a 69 on the dice is your best possible outcome. This allows easier opposed rolls, as the highest roll under skill wins.

Now, thinking about this, you could assign task difficulty on the 100 scale; roll over that assigned number to succeed. That way, if someones skill is too low, they don't have a chance of success... though you could always consider a roll of exactly skill, a critical or automatic success. I think something like this is used in UA for some tasks.

SDLeary

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On one hand, very simple. Roll d100 and add skill to equal or beat a task number. Standard task number is 100.

E.g. Skill 62, task number 100, you need to roll 38 or higher to succeed. For a more difficult task the task number might be 120 or 140. For an easier task the number might be 80 or 60.

Mathematically it's functionally identical to a roll under system.

On the other hand, it completely changes specials, criticals and difficulty modifiers as they are all multiples so you have to reinvent them. For example, succeeding by 50 might be a special.

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I hate to break it to you. But inverted d100 is already out there. First you have Rolemaster but many are scared of by that system (I like it though). Luckily there is a much easier system available called HARP (High Adventure Role Playing) that is not to far from the BRP simplicity. The fantasy rules are currently under revision and will be out again soon, but the Sci-Fi rules have just been released in both print on demand and pdf format and are available.

They are actually second to only the BRP System as my favourite RPG systems and highly recommended.

I noticed that you already was familiar with Rolemaster. But still I think you should give HARP a look if you are after an inverted d100 system.

Edited by Chorpa
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On one hand, very simple. Roll d100 and add skill to equal or beat a task number. Standard task number is 100.

E.g. Skill 62, task number 100, you need to roll 38 or higher to succeed. For a more difficult task the task number might be 120 or 140. For an easier task the number might be 80 or 60.

Mathematically it's functionally identical to a roll under system.

On the other hand, it completely changes specials, criticals and difficulty modifiers as they are all multiples so you have to reinvent them. For example, succeeding by 50 might be a special.

Oh I do like that. It would take a bit of doing, but should be doable to churn out. And with that approach you could grab sample DCs from D&D 3/3.5 and convert them with little difficulty as well, instead of having to decide all the target numbers yourself.

Plus: "Roll over 100" is a damn simple thing to remember, isn't it.

I like that its mechanically equivalent for the basic stuff. As mentioned, specials, criticals and difficulty modifiers may need to be reinvented. But maybe not. As you mentioned, they're multipliers. Maybe I could easily math that out as well, by just multiplying or dividing your bonus to the roll. Hmm.

And I might be able to swap the rolling mechanic without having to change anything else in the system. That's ideal.

I'll have to sit down and take a stab at this.

Thanks! :)

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I think inverting the D100 mechanic would go against the grain of the system, and like already stated, perhaps ICE's Rolemaster or HARP systems may be what you're looking for.

For static rolls in BRP you just apply a Difficulty Modifier according to the circumstances of the situation, this is the current rule. Perhaps you can tweak this a bit so there is a wider variety of mods, having +/- 5% increments to make things 'less static'.

" Sure it's fun, but it is also well known that a D20 roll and an AC is no match against a hefty swing of a D100% and a D20 Hit Location Table!"

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While the d100+numbers part of HARP/Rolemaster is something I like, the rest of the system is slow and clunky, and unsupported. Additionally, I dont want to have all-important classes define your character like you have in rolemaster.

the d100+numbers part of rolemaster - and perhaps the idea of having some sort of crit table (we'll see about that one) are the only real parts of rolemaster I'm interested in.

Theoretically I could leave the rolling mechanic the same, and instead of using multipliers for difficulty I could go with the +-5% method (I think it would yield the same end results as the roll over variant described above), but the numbers might be slower to compare/understand.

When you say "go against the grain of the system" how exactly do you mean? You mean just because its a very noticeable change, or do you mean that it will cause lots of mechanical problems/complications?

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The biggest impact is on the combat system, especially melee combat. Generally speaking, specials and criticals are the crucial moments in a fight and these are based on proportionate chances (1/5 and 1/20 respectively). Changing those to non-multipliers massively changes the dynamic. Say for example, that to get a special result you have to exceed the target number by 40 then someone with a skill of 60 and a target number of 100 will score a special on 80-100, which is to say that 1/3 successful hits are specials as opposed to 1/5. On the other hand, anyone with a skill of 39 or less can't score specials. This is why open-ended rolls then become popular because they give relatively unskilled characters a chance at greater degrees of success. E.g. roll 96-00 means roll again and add. Keep going until you roll 95 or less.

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And I might be able to swap the rolling mechanic without having to change anything else in the system. That's ideal.

No, most likely you will not be able.

As Deleriad said, a lot of the BRP system depends on Degrees of Success: critical beats special beats success beats failure. This is rather important with most skills, but extremely important in combat.

Unless you rework the critical/special system with a lot of painful maths, you will end up with a very different system, where combat becomes suddenly a very deadly affair, or something absolutely impossible to handle without a very high skill.

For instance, the "make it by 50" rule would make it impossible to score a special hit without a skill of 50+. And believe me, two thirds of the fights that beginning characters face in BRP games are resolved by that lucky impale with an arrow shot by a character who has 50% skill or less.

Believe me, there is no "painless" solution to make it roll-over. Either you get accustomed to roll-under, or you accept the fact that you are dealing with a very different (and unplaytested) system.

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A little more granularity in the task difficulties could make the game a little

more flexible and dynamic, but in my view there is a risk to go over the top

with this and to spend too much time on determining the game mechanics

of tasks instead of roleplaying the characters' actions.

One way to handle the problem would be to continue the game's approach

by adding two more difficulty stages:

Automatic: no roll

Simple: 2/1 skill, e.g. a skill of 36 % becomes 72 %

Easy: 5/4 skill, 36 % becomes 45 %

Routine: 1/1 skill

Difficult: 1/2 skill, 36 % becomes 18 %

Formidable:1/4 skill, 36 % becomes 9 %

Impossible: no roll

Add to this the various situational modifiers, and the degree of granularity

should be sufficient for all purposes. Beyond that one would enter the re-

alm of treating each task as an individual one with an individual difficulty,

too complicated and time consuming for my taste.

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These are the task modifiers from LEGEND, they could do the trick for making simple rolls less 'static':

Very Easy: +60%

Easy: +40%

Simple: +20%

Routine: +0%

Difficult: –20%

Hard: –40%

Very Hard: –60%

Formidable: –80%

I love LEGEND, but perhaps the task modifiers are a bit too nit-picky for my liking. They logically work, but I prefer my scale below, more in keeping with BRP ( I just added too values):

Easy: Double listed Skill

Simple: Skill +15%

Routine: Standard Skill roll

Challenging: Skill -15%

Difficult: Half listed Skill

Works for me, but I'm not sure if it's what you're after...

Edited by Mankcam

" Sure it's fun, but it is also well known that a D20 roll and an AC is no match against a hefty swing of a D100% and a D20 Hit Location Table!"

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Thing is, if doing a roll over system then you want the difficulty modifiers to apply to target numbers rather than affecting the skill. Otherwise you remove some of the rationale for using roll over plus target number.

For example: roll under. hard task (-20%) means roll less than equal to skill-20.

Roll-over. Hard task means roll+skill to beat 100+20.

Those two are functionally identical; the question as Mr McStern said, is how do you manage degrees of success (and failure). BRP has 3 degrees of success and 2 degrees of failure and they're all proportional to chance of success. I don't know any way to painlessly (or even painfully) replicate that in a roll-over to beat target number system (RO-TN). The natural way for RO-TN is to is base degree of success on multiples of how much you beat the target number by. (e.g. beat it by 20 is one degree of success, beat it by 40 is two degrees and so on). That's a robust system that's been used in many games but would require a thorough overhaul of BRP degrees of success results because the balance of probabilities is quite different and probably also requires exploding dice. By which time you have to wonder what you've gained.

Edited by deleriad
misleading typo
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Hmm. Perhaps the Legend approach of % modifiers might serve my purposes well enough.

If I were to switch it to Roll Over-TN, I could use the chance of success to determine the degree of success rolled, but I'd have to do math on the fly for that.

Lets say I dont go roll-over, and just want something functionally equivalent to fixed target numbers. Is the list of modifiers from Legend a good way to approach that?

Perhaps take examples of actual tasks (one from each skill or roll type would be the thorough approach) and assign them to the % Modifiers?

I dont mind having a table of modifiers sitting in front of me stuck to my GM Screen.

I don't think the (Skill * x) approach is a good way of modeling difficulty. IMO that models the degree to which skill is more relevant than chance, as opposed to the difficulty of a task.

I'm curious about that one variant rule that was mentioned though, the price is right model (higher is better unless you go over), where is that spelled out? I can see it speeding up play.

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I was looking into this some time ago, and from what I remember a target of 100 with all modifiers added to the actual D100 roll works best. It has the advantage of being open-ended, and some people just like to roll high for success.

However, it's very different from BRP, so you would basically have to replace the whole skill system. Probably doable, but you'd have to judge for yourself whether the work would be worth it.

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I'm curious about that one variant rule that was mentioned though, the price is right model (higher is better unless you go over), where is that spelled out? I can see it speeding up play.

Basically, it is how all Opposed rolls work, especially in Legend. You win if you score a degree of success higher than your opponent (you crit and he succeeds, you succeed and it fails). If the DoS is the same, the highest roll wins. Legend combat revolves around this concept, as defense rolls are not opposed, but rolls to resist the effects of damage are: you have to beat the attack roll with Resilience, or else you go down.

Hmmmmmmmmmmm.....

You have just given me a SUPER idea.

No more "minus" modifiers to skill. Just use the static number like a roll you have to beat with your own roll. So instead of "roll your skill -20", it becomes "Beat 20 with your skill, that is any success higher than 20 wins". This can be a really, really good variant rule to go with "standard" BRP. The only drawback is that it does not work very well with positive modifiers. But BRP has very few positive modifiers, when you want to give an edge to a character you usually double his skill.

Moreover, a +20 modifier may be simulated with a "Beat a failure of 80" mechanics. Any failure above 80 wins anyway.

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I dont mind having a table of modifiers sitting in front of me stuck to my GM Screen.

Then it should not be such a big deal: if you absolutely want to use the roll over procedure, since high rolls are good and low rolls are bad, in the contrary to the BRP, make a new critical, special and fumble table simply by subtracting the BRP required roll to 101:

Ex: with a 80% skill, critical 01-04, fumble 99-00, special 05-16 becomes critical [101-(01-04) = 97-00], fumble [101-(99-00)=01-02] and special [101-(16) = 85-96].

The question is: what if I have a difficulty of 120? Then take the amount above 100 (here 20) and read on your table the fumble and critical values for [skill rating] minus [amount above 100 (in our example 80-20=60), and you get it.

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You have just given me a SUPER idea.

No more "minus" modifiers to skill. Just use the static number like a roll you have to beat with your own roll. So instead of "roll your skill -20", it becomes "Beat 20 with your skill, that is any success higher than 20 wins". This can be a really, really good variant rule to go with "standard" BRP. The only drawback is that it does not work very well with positive modifiers. But BRP has very few positive modifiers, when you want to give an edge to a character you usually double his skill.

Moreover, a +20 modifier may be simulated with a "Beat a failure of 80" mechanics. Any failure above 80 wins anyway.

I think I like this idea. That seems like a decent way to represent "This Rope is X Hard to climb" As opposed to "How good are you at climbing?"

That seems like it would be equivalent to actually changing the mechanic to a roll over + stuff, but without breaking the other systems or complicating things for the PCs.

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Basically, it is how all Opposed rolls work, especially in Legend. You win if you score a degree of success higher than your opponent (you crit and he succeeds, you succeed and it fails). If the DoS is the same, the highest roll wins. Legend combat revolves around this concept, as defense rolls are not opposed, but rolls to resist the effects of damage are: you have to beat the attack roll with Resilience, or else you go down.

Hmmmmmmmmmmm.....

You have just given me a SUPER idea.

No more "minus" modifiers to skill. Just use the static number like a roll you have to beat with your own roll. So instead of "roll your skill -20", it becomes "Beat 20 with your skill, that is any success higher than 20 wins". This can be a really, really good variant rule to go with "standard" BRP. The only drawback is that it does not work very well with positive modifiers. But BRP has very few positive modifiers, when you want to give an edge to a character you usually double his skill.

Moreover, a +20 modifier may be simulated with a "Beat a failure of 80" mechanics. Any failure above 80 wins anyway.

We are thinking across similar lines...

SDLeary

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Yes, but you do not need to change critical and special ranges. A crit is still a very low roll.

Let us see what happens if you are 50% and you have to beat a roll of 20.

if you roll 01-10, you succeed because you special. You automatically beat the difficulty.

If you roll 11-20, you fail because it is a success, but lower than the target.

If you roll 21-50, you succeed because it is a success and you beat the target.

With 51-00, you just fail.

The advantage of this is that it works exactly the same way when you have to beat a skill, that is a dynamic roll.

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Aces and Eights uses the inverted (i.e. roll percentiles and try to roll high) system. Skills start high and the more you improve them, the lower they go.

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There are several problems with the "beat" a number approach. It gets used in Legend quite a lot for delayed and indirectly opposed rolls (i.e. where one roll is later than the other or can't actually affect the other.)

For me the most significant difference is that it doesn't change the critical or special chance which means that your proportion of specials to normals changes significantly.

E.g. Your skill is 40%. You have to beat a number of 40. This means that every success is either a special or critical. So if you have poorly skilled person vs a number created by a highly skilled person then every victory by the poorly skilled person has an extra benefit of being a special or critical. There's also the reverse issue of what happens when someone with a skill of say 140% faces a number of 40? The extra 40% is *somewhat* lost.

For those reasons I prefer a standard skill modifier. Admittedly I don't like multipliers and never use them. I also don't particularly like stacking modifiers so I prefer to use a version of OpenQuest's big, unstacking modifiers. (Basically +20, +40 and +60, and -20, -40, -60, -80)

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Yes, but you do not need to change critical and special ranges. A crit is still a very low roll.

Let us see what happens if you are 50% and you have to beat a roll of 20.

if you roll 01-10, you succeed because you special. You automatically beat the difficulty.

If you roll 11-20, you fail because it is a success, but lower than the target.

If you roll 21-50, you succeed because it is a success and you beat the target.

With 51-00, you just fail.

The advantage of this is that it works exactly the same way when you have to beat a skill, that is a dynamic roll.

Ah, yes. I was figuring on using an alternate for specials and criticals. Perhaps doubles for specials and skill match for critical.

I recall a method, like what your proposing, being mentioned someplace else before. IIRC, it was decided not to use it because it felt that it would cause confusion because the goal was both to roll high under skill and to roll low for criticals and specials.

SDLeary

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I really like alot of the BRP Stuff I've been reading; but I'm not a big fan of the roll under mechanic. I think it works great for opposed tasks, but works less well for static tasks. I dislike that you're essentially rolling against your own skill, instead of rolling against the difficulty of the task.

Since you like BRP 'd100 roll under' for some things (opposed rolls <spit>), the proposed "Inversion" to RoleMaster-style 'roll over' seems like a much more drastic change than really necessary. (And would create a hybrid system, essentially d20-style but rolled on d100). To me, that wouldn't be BRP at all, or even proper d100.

So what's wrong with 'rolling against your own skill'? I think that's a major good aspect of BRP-type systems.

There are plenty of degrees of difficulty that can be set, so it's not always the same % as your skill, by a long chalk. Some tasks will be Easy (x2) or Hard (x1/2), or (virtually) Automatic or Impossible (I sometimes call for x10 or x1/10 rolls for these). Your thread has made me realize, though, that we don't only have those levels of difficulty - I'm sure it's common practice to say some tasks require a Special (1/5th) or even a Critical (1/20th) success. So there are plenty of 'degrees of success', plenty of 'targets' that can be set.

Might what's really needed here be a translation between D&D-style target numbers and the task's requirement for Easy/Standard/Hard and/or Normal/Special/Critical rolls?

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I guess I'm a little sketchy on the "multiplier" mechanic, in a "skeptical towards liking it" sort of way.

Multiplying your skill, to me, isn't the same thing as setting a difficulty, because it affects people of different levels of skill quite differently. Instead, it's determining how much *any* person stands a chance of success, and more skilled people are affected by a greater % than lesser skilled people. The difficulty of the task varies depending on who is attempting it. And that to me seems, well, illogical. Not only does my skill affect how easily I can accomplish it, it also makes the task itself vary in difficulty.

Some sort of translation may work, maybe, but skill multipliers & dividers just seem like the wrong way to approach task difficulty to me.

If that mountain cliff isn't changing itself depending on who approaches it, then multipliers dont make alot of sense to me as the mechanism to say how hard it is; they dont affect everyone evenly. Now if climbing the mountain cliff is deemed a -20% modifier, then that mountain is straight up 20% more difficult than the 0 modifier task, regardless of who is trying to climb it.

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