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Should I go from Percentiles to D10?

Started by Rob Lang, June 08, 2007, 05:02:58 AM

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Rob Lang

Something that's been bugging me for some time is the skill percentile system in Icar. Generally, it's not very easy to use. For the uninitiated, every skill has a percentage and to pass it, you have to roll 2 D10 under it. Now, I've always argued that it's quite easy to roll under something because you don't need to do any sums, you just compare. Is 22 (on the dice) less than 67% (on the skill)? Yes! Quite quick and simple.

The problem comes with modifiers and difficulties. I find myself having to ask how far under the skill the roll was more often than not. It's no longer simple comparison but brain-aching set of 2-figure subtractions and additions.

I'll give an example:
You have Heavy Firing skill of 67%. You're shooting someone at short range with a weapon that has a modifier of 20%. Therefore, your target number is 87%. That should be written on the weapon sheet you're using, so it should be simple to check so so far. But then you're trying to do something complicated, so you get a 55% modifier. Now you have to take away that from 87%. Bit of a pain, isn't it.

The Proposal
Some of you can see what's coming, no doubt. Divide the percentiles by 10. This would make the skill ranges 1-10, rather than 1 to 90%. Here's how the rules would be set up:

  • Every skill is from 1-10.
  • You have to roll under the skill value to pass.
  • 10s are automatic fails (same as for Stat checks at the moment)
  • 1s are automatic passes (same as for Stat checks at the moment)
  • Difficulty levels will be reduced like they are for Stats at the moment
  • 3 Roleplaying Points (read XP) needed to raise a skill, but only if ticked.
  • (Under playtest) 4 Roleplaying Points and a good explanation needed to tenuously raise a skill if not ticked.
  • The starting values for First Epoch skills will be based on a single Statistics. You get 1 if you stat is between 1-5 and 2 if your stat is 6 or more.
  • Second epoch skills (one step up the skill tree) start at the previous epoch -3.

The Pros are that the maths becomes much easier. Our example above, (with adjustment) becomes a skill of 8, a modifier of 2, makes 10 and then you get a -6 modifier to that. Making 4. That's what you have to roll under on a D10. Much easier mathematics.

Furthermore, vehicle combat becomes much easier as there will be no need to divide by 10. The manouvre roll becomes Skill + D10 + Manouevre of Vehicle + Manouvre you're doing.

The Cons are that this is a lot of work. All the rules will need to change and all the equipment sheets will need updating (and rebalancing in some places).

Before I plum for this, I really do need some feedback and thoughts. I don't think it as a major change of feel, just a simplifying step but that's only because I've been listening to roleplaying podcasts and got my head full of newfangled ideas. Please let me know your frank opinions!

RPGPundit

Do you use modifiers that are in less than increments of 10? Is there stuff right now that can cause a +5 or -5 modifier? If so, you really probably don't want to change your system.
If not, if the smallest modifier is +/-10, then you're good to go.

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Rob Lang

It's a good question, Pundit and one I have pondered. There are modifiers of +/-5 but they are rarely used. There isn't a case, for example, where there are a set of modifiers such as 10,15,20,25,30,35 and so on that are all distinct. There are the odd 5/15 ones but they are rare. I think I may have subconsciously steered away from them due to the subsequent difficulty of the maths!

My RPG group have been playing Icar for many years, so they are used to doing 2-number maths but I am really interested in the overall opinion of the rest of you lovely roleplayer types.

Warthur

Personally, I like percentile systems because of the granularity. Even if all the example modifiers in the rulebook are in increments of +/-5, I like being able to compromise and say "Hmmm, well that's obviously worse than this -5 penalty, but I don't think it's as bad as this -10 one - let's call it -7."

Having room for negotiation is nice.
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Skyrock

In the case of 5-step increments you might want to settle for a d20 instead of a d10. That should do the trick without any further tinkering with the modifiers.

I never liked percentile systems which are fine-granular for the sake of fine-granularity. I'm also not a fan of modifier-fudging as Warthur suggests - tossing around freeform modifiers off the top of my head isn't work that I want to do as GM.
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Hackmaster

I loved the old percentile system in Rolemaster/Spacemaster. When we did play, however, a lot of players used calculators to help with the math. To wit, it was quicker for them to add and subtract two digit numbers on a calculator than in their head. That being said, I don't think any game designer really ever envisions people sitting around playing their game with calculators. Therein lies the danger of percentile systems that don't stick to numbers that are multiples of 5 or 10.

I don't like the 1d10 idea at all, it seems the range is too limited, especially when you throw in automatic success and failure. A good substitute for d100 is the d20, giving the same distribution in 5% increments. The downside is a few people have this weird hate of D&D/D20 and don't like any games that use a d20. Personally, I find it makes for a nice d100 replacement.

What I really like are simple bell curve rolls like 2d6 or 2d10. 2d10 makes a decent percentile replacement giving a 2-20 range and cuts down on the extreme rolls due to the bell curve.

My suggestions summarized:
1. The easiest thing for you to do with the least amount of changes would be to go back and tweak the game so all numbers in your percentile system are multiples of 5. This makes the math a little easier for some.
2. Try a d20
3. Try 2d10
 

flyingmice

I'll second GoOrange's suggestions, Rob, and for the same reasons.

-clash
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HinterWelt

See, I have had a similar request by a few customers. They would prefer the percentile system for Iridium to be aligned with the stats (d20 range) and I have shown them how easy it is to convert. I really should put a converting faq up.

Still, my suggestion would be to review your system and honestly ask yourself if it works
1. smoothly
2. within the intention of your design

Sometimes you will need to sacrifice smooth play for the design of your game and other times the opposite. In the end, you always hope you have the most pleasant play experience combined with a balanced and functional system.

As to the implementation, I would suggest a d20 conversion as others have mentioned if at all possible. Also, consider making it open ended which will help with range of your rolls.

Good luck,
Bill
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flyingmice

Let me make my post more clear, because I didn't say what I meant to say.

No one loves percentiles more than I do. They are clear, instantly understandable, and easy to use. IMO they bring more positives than negatives to the table. However, if you have determined to change ICAR to something else, GoOrange lists - in order - the best solutions for you.

There is another possibility - abstraction with multiple optional task resolution sub-systems. When I designed the StarCluster system, I put in a layer of abstraction, so that things weren't directly referred to in percentile. You had to do a quick conversion into percentiles - for example skills are ranked at +1, +2, +3, etc., and you add 5% per rank to to 40% to find your actual skill percentage. By changing 5% per rank to 1 per rank, and 40% to 8, you can run the game with a d20 rollunder, or 2d10 rollunder. I'm now working on several other optional t-r systems which use the same character generation systems, but work with d20 die pools, 4d6-4 rollover, and even diceless. It's the work of a couple of minutes or so to convert back and forth. When I'm done, fans will be able to play any SC game with a huge variety of t-r systems, whatever they prefer.

Remember, ICAR is free, so the only person you really have to satisfy is yourself.

-clash
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RPGPundit

Personally, it feels to me like a 1-10 success range is a little too constricting.  That was my question regarding modifiers for you: the real question is whether you are already basically working on a 1-10 scale, or whether you are actually working on 1-20 scale (ie. 5% increments) or whether you are working on a full-blown 1-100 scale.

It would seem to me that a 1-10 scale would make it difficult to create "smaller" modifiers, it would allow too much randomness if you tried to have a critical/fumble rule (or even an automatic success/automatic failure rule), and might have other issues.

But then, if that's already what your system is like, that whole argument becomes irrelevant unless you actually want to remake the system entirely.

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NOW AVAILABLE: AoI in print form

LORDS OF OLYMPUS
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HinterWelt

Quote from: flyingmiceLet me make my post more clear, because I didn't say what I meant to say.

No one loves percentiles more than I do. They are clear, instantly understandable, and easy to use. IMO they bring more positives than negatives to the table. However, if you have determined to change ICAR to something else, GoOrange lists - in order - the best solutions for you.

There is another possibility - abstraction with multiple optional task resolution sub-systems. When I designed the StarCluster system, I put in a layer of abstraction, so that things weren't directly referred to in percentile. You had to do a quick conversion into percentiles - for example skills are ranked at +1, +2, +3, etc., and you add 5% per rank to to 40% to find your actual skill percentage. By changing 5% per rank to 1 per rank, and 40% to 8, you can run the game with a d20 rollunder, or 2d10 rollunder. I'm now working on several other optional t-r systems which use the same character generation systems, but work with d20 die pools, 4d6-4 rollover, and even diceless. It's the work of a couple of minutes or so to convert back and forth. When I'm done, fans will be able to play any SC game with a huge variety of t-r systems, whatever they prefer.

Remember, ICAR is free, so the only person you really have to satisfy is yourself.

-clash
And see, this is much like what I was looking at for Iridium. The difference is, and it makes it a bit more difficult, that I do not have a linear progression in my skill ranks. Also, once you get beyond five ranks in skills you probress at 2% and after 10 ranks you progress at 1%. So, some snags are there. In making Iridium Lite, I dealt with this by capping skills at 5 ranks. However, more than that, I went to a more linear system. With IL, you have Rank + Stat + Aptitude for your target roll under number. The potential is to max out at 21 but since I have an open rolling system (even with d20) you still have a chance for failure.

Long story short, I would still advise an open end roll.

Bill
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algauble

One idea for keeping the percentile system would be to use the penalties as target numbers to beat, so if you have a skill of 87% and a difficulty of 20 then any roll of 21-87 would be a success, and any roll of 01-20 or 88-00 would be a failure.
Some people object to this since they would prefer high or low rolls to consistently always be better, while this set-up makes low and high rolls bad, depending on difficulties and skill levels.
It also presents potential problems with degrees of success (BRP/RQ style criticals/specials, for example).
But it is math-free at the table.
-al

Rob Lang

First of all:

Thanks everyone for a fabulous set of well reasoned feedback!

It's given me lots of things to think about. I'm collating ideas, information and opinions from a range of sources. Be they "Swine", Hard Bitten Icar Veterans or you free thinking radicals. Thanks to all the feedback, I've managed to better define what it is I want from Icar.

1. I want it to be more accessible.
2. I want it to have less mathematics for the majority of action resolutions.
3. I want to retain some degree of granularity so that advancement may be gradual.
4. I want it to be quicker.
5. I want it to be different.

As a wise man once said about the very dodgy Icar version 2.x "The system matters for shit, it's the setting that's different", so (5) is safe, regardless. I'm not going to go avant guard and be using a Ouija board for conflict resolution.

So, it is time to dump the percentiles.

Thanks for pointing out that the granularity for d10 isn't very intuitive. I'll avoid that.

I quite like the idea of d20 and am not concerned about it being similar to other systems. Having a skill in the 20 range is good but granularity will be sacrificed - not ideal for Icar, which is really designed for campaigns.

Being a bit keen on statistics mathematics, I do like adding two D10 together for a bell curve, making the extremes less likely. Nice.

I do like the idea of having a percentile with the difficulty giving the lower band. It's still comparable and I normally give difficulty. Doing a comparison there is quick and you don't lose granularity. As mentioned, you lose the degree of pass/fail but that doesn't matter in Icar.

So, the two big contenders are:

  • 2D10s with a skill range of 3 to 20. Three skill uses in separate sessions allows a skill raise.
  • Retain percentiles and have the difficulty set as the lower boundary. Anything in this range is a pass. Everything else remains the same.

I'm going to trial both with my weekly game session and see what we think. However, it won't be the most unbiased test ever! I'll let you know what we find out.

Many thanks again for the help!

Rob Lang

My brain just started working again!

Actually, retaining the percentiles might not work very well because the characters might get modifiers that push their skill over 100. The difficulty then brings it back into the range where you can roll. If you're using the lower limit difficulty level then you can't roll.

For example:
Current Way:
Skill level: 90. Various benefits:+30. Pushes the skill to 120. Trying something difficulty: 50. Now need to roll under: 90+30-50 = 70.

Lower limit way:
Roll above 50 and below 120. Ah.

So, you'd need to do mathematics anyway. It's a pity because I really began to like that idea.

algauble

Quote from: Rob LangMy brain just started working again!

Actually, retaining the percentiles might not work very well because the characters might get modifiers that push their skill over 100. The difficulty then brings it back into the range where you can roll. If you're using the lower limit difficulty level then you can't roll.

For example:
Current Way:
Skill level: 90. Various benefits:+30. Pushes the skill to 120. Trying something difficulty: 50. Now need to roll under: 90+30-50 = 70.

Lower limit way:
Roll above 50 and below 120. Ah.

So, you'd need to do mathematics anyway. It's a pity because I really began to like that idea.

Well, you could have your (skill minus 100) introduce a new success range at the low end of the dice range.  Using your example B, a roll of 01-20 = success, 21-50 = fail, 51+ = success.

For opposed rolls, you could say that your (skill minus 100) is your opponent's target number (or added to their target number).  RQ2 did something like this, but with the amount over 100 subtracted from the opponents skill percentiles.