Can Percentile Work?

Oniros25

I'm working on a game of my own. I currently have no aspirations of selling it or even giving it away to people I don't know. I just want it to be the best game it can be. Currently, I'm running everything through a percentile-based setup with the d100 as the only roll made. I mentioned this on a recent article over at the PAR and it was brought to my attention that percentile is cumbersome for mental math and therefore somewhat undesireable. So, does anyone like percentile based games or think the model has potential or is it pretty much unanimously reviled? Does anyone have examples where they saw it used really well? Really poorly?

As it stands, if my group likes it, that's all that matters, but I think it could be something that I would like to bring to the world at large someday. Just looking to see just how much I'm going to laughed at if I do so...

Dex Dynamo

@DE?AD uses a percentile system for the Glossalia games (core rules here), and has been using them for some time, and would probably be the authority on the subject.

DE?AD

I love percentile systems in concept, hence, as Dex said, my using it in my homebrew stuff. It is totally true that the mental math can get cumbersome, though.

For my own purposes I've stuck to a really simple system of "it feels right". I have Traits that are more guidelines to come up with a percentile goal than numeric bonuses applied to rolls.

If you were gonna go the specific, numeric route, then I'd say stick to broad categories. Something like "Great Circumstances +20%", "Good Circumstances +10%", "Bad Circumstances -10%", etc., instead of "Partial Cover -15%", "Low visibility -10%", and the like.

Oniros25

DE?AD wrote: »

I love percentile systems in concept, hence, as Dex said, my using it in my homebrew stuff. It is totally true that the mental math can get cumbersome, though.

For my own purposes I've stuck to a really simple system of "it feels right". I have Traits that are more guidelines to come up with a percentile goal than numeric bonuses applied to rolls.

If you were gonna go the specific, numeric route, then I'd say stick to broad categories. Something like "Great Circumstances +20%", "Good Circumstances +10%", "Bad Circumstances -10%", etc., instead of "Partial Cover -15%", "Low visibility -10%", and the like.

Not entirely sure what that means. I'll have to look at your core rules thingy when I'm not at work to see if I can illuminate myself. I'm already using the "broad categories" tactic that you described, so maybe it can be manageable at least. *sigh* I just really love this game I'm building and I don't want it to be DOA if I do decide to see if it can have some sort of life beyond my kitchen table.

Inquisitor

Call of Cthulhu and Dark Heresy both run using d100s and work just fine.

Oniros25

Inquisitor wrote: »

Call of Cthulhu and Dark Heresy both run using d100s and work just fine.

That's an excellent point. I was inspired by Call a goodly ammount in the construction of my game. I haven't looked at Dark Heresy yet since I'm not big into Warhammer 40k, but maybe I'll give it a look just for the chance of plundering anything extra clever from its pages.

OptimusZed

I don't think there's anything inherently bad about percentiles, at least when compared with other linear dice resolution methods.

It's a matter of making sure the system doesn't get in the way of the game, just like every other type of system.

CesareB

I think the problem with percentile is that it sometimes feels unnecessary. How often is it really beneficial to make a distinction between an 87% chance of success and an 85% chance? If you don't feel that necessity, then d10 or d20 is good enough without being fussy.

PMAvers

Yes. Yes it can.

Fleur de Alys

A big risk with percentile is that it drives the designer to want to make the most out of its most apparent advantage: the ability to apply modifiers at the 1% level of granularity. On the surface this seems great; you can put small modifiers on things without worrying about the massive impact that same modifier would have on, say, a d20. However, this can lead to the game including way too many modifiers, and that's where you enter "cumbersome" territory.

Instead, I'd offer that percentile's main advantage is in how it handles games where the default "chance of success" of a given action is high. For example, if you assume that the average attack has an 80% chance to hit, you can offer players up to +19 on their roll before you enter "can't fail" territory. If you were using a d20 with a base 80% chance, then the actor only needs a roll of 5 or higher on the dice, and a mere +4 now puts things firmly in the No-Fail Zone.

So if we compare this to D&D, a percentile system with a high base chance of success gives you a more deterministic game while still allowing for approximately the same amount of modifiers.

Grunt's Ghosts

If you look at Eclipse Phase, which uses a d100 system, they have it where the modifiers can't go over +/-60.

Oniros25

The Sauce wrote: »

A big risk with percentile is that it drives the designer to want to make the most out of its most apparent advantage: the ability to apply modifiers at the 1% level of granularity. On the surface this seems great; you can put small modifiers on things without worrying about the massive impact that same modifier would have on, say, a d20. However, this can lead to the game including way too many modifiers, and that's where you enter "cumbersome" territory.

Instead, I'd offer that percentile's main advantage is in how it handles games where the default "chance of success" of a given action is high. For example, if you assume that the average attack has an 80% chance to hit, you can offer players up to +19 on their roll before you enter "can't fail" territory. If you were using a d20 with a base 80% chance, then the actor only needs a roll of 5 or higher on the dice, and a mere +4 now puts things firmly in the No-Fail Zone.

So if we compare this to D&D, a percentile system with a high base chance of success gives you a more deterministic game while still allowing for approximately the same amount of modifiers.

That's actually a very interesting way of looking at it. I wasn't using 1% granularity anyway (that way seems to lead to tons of nickle-and-dime bonuses and penalties that get henious to keep track of.) Chance of success does tend to be high in my game though. I'll have to look into utilizing it as you describe.

Grunt's Ghosts wrote: »

If you look at Eclipse Phase, which uses a d100 system, they have it where the modifiers can't go over +/-60.

I have a similar rule. Good to know it's a good one.

OptimusZed

Oniros25 wrote: »

Grunt's Ghosts wrote: »

If you look at Eclipse Phase, which uses a d100 system, they have it where the modifiers can't go over +/-60.

I have a similar rule. Good to know it's a good one.

Well, it's one used in Eclipse Phase, anyway.

Not sure one follows directly from the other.

Grunt's Ghosts

When I was coming up with a system for my game, I was looking for something that felt fast since my setting is a swashbuckler/steampunk/sky pirates/DnDfantasy. While I thought about using the Fate/MHR system for the freedom it allowed in character concepts, I've gone with a d100 with a splash of d20 Modern mixed in with feats, spells, and races. Its not done yet (nor in a working state because I've been lazy/busy/drunk) but so far everything I've made seems like it will work smoothly once all the parts are in place.

Oniros25

Grunt's Ghosts wrote: »

When I was coming up with a system for my game, I was looking for something that felt fast since my setting is a swashbuckler/steampunk/sky pirates/DnDfantasy. While I thought about using the Fate/MHR system for the freedom it allowed in character concepts, I've gone with a d100 with a splash of d20 Modern mixed in with feats, spells, and races. Its not done yet (nor in a working state because I've been lazy/busy/drunk) but so far everything I've made seems like it will work smoothly once all the parts are in place.

That's cool and sounds really fun. Have you been playtesting? I have been playtesting mine with my group, but I realized recently that one of my players is kind of a human calculator and may have been running all the mental math for me and my whole group (he's good at sneaking information like that in without you noticing he's feeding it to you.) I'll have to watch to make sure he's crunching just his numbers and see how the others do next time.

Mine is a stealth tactical fantasy game caste from the same stuff as videogames like Thief, Dishonored and, to a much lesser degree, Metal Gear. I've had players describe it as Steampunk Shadowrun which is an oversimplification, but not entirely inaccurate. The reason I went percentile in the first place was I needed the flexibility of it for the stealth related stuff while keeping abosultely everything around it as simple as I possibly can in order to make that stealth system sing in the way I knew it could. I'm rightly proud that I've gotten what I have running since when I first set out on this road, I was told repeatedly that what I was attempting just couldn't be done. They said I was mad. But I'll show them. I'll show them all!!!!

...sorry, inner mad scientist leaked out there for a second.

Grunt's Ghosts

I haven't playtested it yet (I'm still righting up the skills which I keep adding to and subtracting from, last count it was at 52, most its been is 70) but once I get some more work done I might do a Roll20 playtest here.