Percentage-based games

[Space Cowboy]

Hey all,

I was asked to do a guest column for RPG.net on the conceptual and developmental history of Wild Sphere, an RPG I'm in the middle of writing.  I'm finishing up the guest column and wanted to add a bit more about WS' task resolution mechanic, which revolves around percentage rolls.  I wanted to know, other than Chaosium's BRP, what other percentage-based games are out there, and their strengths and weaknesses.

To take a look at the Core Mechanic or for more information about Wild Sphere in general, please come to visit our website at

http://www.wildsphere.com/

Many thanks in advance!

[Bret Gillan]

If I remember correctly, the TSR's now out-of-print Amazing Engine system used percentile rolls.

Or were you looking more for systems currently in use?

[Uccisore]

Unknown Armies is basically percentage based, and Star Frontiers was, back in the day.  They both share the same weakness as does BRP: You need alternate rules to handle anything radically more or less powerful than a human being.  If a max-strengthed human being is operating in the 80-90th percentile, then how do you handle a grizzly bear or elephant?
    The perk to a percentage based system is that it can be understood almost instantly, and is intuitive to even non-roleplayers.
    Are you looking for any other sorts of comments about the rules or how they are written? I have a couple suggestions, but I don't want to criticize if you aren't here for that. ;)

[TRance Junkie]

still going and very mainstream - call of cthulhu is a percentage based system.

Characters are essentially a list of skills e.g. Spot hidden 75%. Modifiers are generally not used, so you would have a 75% chance every time you want to spot something which is hidden or obscure.

Adavantages are that it's extremely easy to use.

Limitations are that if you want to do something for which there isn't a skill listed then you've got a bit of problem - you have to define it as a new skill then assign a default percentage (which takes no account of the other skills you might have) - got 90% in horse riding, but not got ride camel that'll be 10% then...

If you've got a high skill you will virtually always succeed, conversely you're very likely to fail if you've got a low score - events in the game are often too certain.

Secondly the system as written emphasises just a few skills - so having high skills in those is essential to doing well in the game.

The character improvement system has quite a nice feel - it's based on the idea that you tick boxes and then make a roll where you try and fail i.e. it'e easy to improve in something you're not good at.

[Kedamono]

Tri Tac Games used percentage based rolls for skill resolution, in their Bureau 13: Stalking the Night Fantastic, Fringeworthy, FTL:2448, and Incursion RPGs.

In fact in each game there were many parts, especially the damage allocation system, that were percentage based.

[JMendes]

Ahoy, :)

Also, Rolemaster may be thought of as fitting this cattegory, although it's an exploding d%.

Cheers,

J.

[Trevis Martin]

All of the Palladium Games - Palladium Fantasy, Mechanoids, Rifts, Robotech, TMNT, etc.  Used the same percentile based system.

best

Trevis

[Space Cowboy]

Hey guys,

Thanks heaps for your posts!  Lots of stuff for me to take a look at.

Uccisore, if you or others have any suggestions on our Core Mechanic, please let me know!

Trevis, lol, forgot about Palladium.  I have to go take a look at my copy of "Rifts".

If anyelse has ideas, please let me know.

Cheers

[Jules Morley]

Some slightly less mainstream games:

Judge Dredd (Games Workshop, sometime in the 80s) was a % system, with only six skills. But hey, it was based on a comic franchise. :)

Twilight 2000 (Game Designer's Workshop - first edition) was % skills. Second Edition tried to simplify it by going to d20.

Paranoia (West End Games - first edition) was also % skills. Again, I think they went to d20 for second edition (d20 meaning 'use skills in 5-point increments' rather than the current meaning of 'use the d20 based-off-D&D system pimped by WotC et al').

[efindel]

Bushido is an oddity in that it had percentage-rated skills, but used a d20 for resolution (skill level divided by 5 plus an attribute modifier gave a bonus to the d20 roll).

FASA's house system, used for their Star Trek and Dr. Who RPGs, used percentage-rated skills (and ability scores), and used percentile dice for resolution in pressure situations.  In non-pressure situations, one needed to roll 1d10 and get under the skill rating... with the result that while a 10 was all one needed to be "minimally competent" at something, you still had a lot of room to grow from with it.  (At least, it had that rule in the ST version... never actually got to read the Dr. Who one completely.)

TSR's original Top Secret used percentage-rated skills and abilities, and used percentiles for skill rolls and a bunch of other stuff.

Also with TSR, Marvel SuperHeroes, Conan, and one edition of Gamma World all used a "Universal Table", with percentile dice used for rolling on it.  PaceSetter's house system (used for Chill, TimeMaster, and Star Ace) did as well.  Lost Souls, from Sage Lore Productions, did another variation on the same theme.

Victory Games' James Bond 007 did an interesting variant.  Skills and attributes were both rated with fairly small numbers (in the 1-10 range usually, never above 20 that I recall seeing).  (Attribute + Skill) times an "Ease Factor" from 1/2 to 10 was used as the chance of success, with percentile dice.

Millennium's End is a fairly standard percentile system, although it adds some neat wrinkles to combat.

HarnMaster is a percentile system, with the wrinkle that any roll that ends in a 0 or 5 is "critical" (success or failure, depending on whether the roll itself was success or failure).  This makes "criticals" be approximately 20% of all rolls without any complicated math.

... and that's all that springs to mind.  Whew.

[Walt Freitag]

And let's not forget that early editions of AD&D used a huge number of different percentile rolls, including modifiers expressed as +/- percentage points, for many types of events, including thief skills, assassinations, morale checks, reaction checks, magic item fabrication, and magic resistance. It also had very many specific percentile rolls (sometimes with modifiers, sometimes without them) for specific situations, spells, items, monster characteristics, and monster behavior, often in the form of "X% chance that A happens, Y% chance that B happens instead, etc." or in the form of "X% chance +/- Y% per (variable, such as spell caster level) of getting a certain result." Take away character stat rolls, rolls to determine hit points, saving throws, to-hit rolls, and damage rolls, and what's left is pretty much a percentile-based system (or perhaps, rather, a huge assemblage of unsystematized special percentile rolls).

- Walt

[Space Cowboy]

Hey guys,

Thanks for your posts!  Hey Jules, yeah, I'd forgotten about those old school games like T2000.  

Enfindel, was FASA's Mechwarrior percentage?  All I remember is that they used a point-build CharGen.

Walt, hey a fellow Bay Stater! (although I'm an ex-pat in California)

Cheers

[efindel]

Enfindel, was FASA's Mechwarrior percentage?  All I remember is that they used a point-build CharGen.

Dunno... never read or played that one.