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RPG Laboratory

Universal Percentile System

Just wanted to get some input on a new game system I'm slowly fleshing out.
Basically, I've been pondering a percentile-based RPG system that requires only ten-sided dice to be played, though a calculator will be necessary as well. I actually like the calculator as a game tool, as most RPGs don't rely on calculators, and the system I've been thinking of could make use of one with out getting too complicated in the calculations.

The system I've been working on is tentatively titled the Universal Percentile System, or UPS. Rather than having percentile-based statistics, it will instead have non-percentile statistics. The percentiles will come into play when statistics are compared to each other as ratios. These ratios will determine chance of success or failure.
Perhaps it'd be better if I talked in specifics rather than in general terms. Here's what I have so far for the Universal Percentile System:

Characters have four basic statistics: Adroitness, Might, Intelligence, and Will. Two ten-sided dice are rolled and added together to determine each basic statistic when the character is created. Adroitness is physical quickness, Might is physical strength, Intelligence is mental quickness, and Will is mental strength.
Once the four basic statistics are determined, the three secondary statistics are determined. The three secondary statistics are Physical, Spiritual, and Viability. Physical is determined by adding Adroitness and Might together. Spiritual is determined by adding Intelligence and Will together. Viability is determined by adding Physical and Spiritual, then dividing the result by two (round up).

Once these statistics are determined they are used to decide all gameplay. The chance of an action succeeding or failing depends upon the statistic of a character matched against an opposing number, which will either be a difficulty number determined by the GM or will be the statistic of an opposing character/creature. The formula used to calculate success is as follows: Add the character's statistic to the opposing number, then divide the character's statistic by the total to get the percentage chance of success. Mathematically, this can be expressed as (Character's statistic) divided by (Character's statistic + opposing number). This of course is where the calculator comes in, as the result of the division must be converted into a percentage chance.
For example, let's suppose a character is fighting hand-to-hand with another character. When determining if a strike hits, the statistic used by the attacking character will be Physical, and the opposing number will be the defending character's Physical. Suppose both characters are evenly matched with Physicals of 15. The chance for the attacking character to hit is 15 divided by 30 (which is 15 + 15), which equates to .50 or 50%. This means that two equally matched individuals have a 50/50 chance of hitting each other in combat... makes sense to me, or at least gives me some basis to say the ratio/percentile system I'm working on has some logic to it worthy of a realistic game system.

As far as damage goes in combat, weapons will do a certain amount of damage that is then compared to the target's Viability to determine a percentile chance of wounding the target. For instance, a weapon that does 10 damage to a character with Viability of 20 has a 33% chance of wounding (10 divided by 30, using the ratio determining equation for conflict resolution). If a wound roll succeeds, the target gains a wound factor. For each 10% a wound roll succeeds by, an extra wound factor is gained. I haven't fleshed it out yet, but wound factors will cumulatively harm a character/creature worse and worse the higher the wound factors go, until death occurs, of course.

So, I have a basic system for combat using the above rules. Spiritual combat can occur as well, only using the Spiritual in place of Physical. Non-combat conflicts will occur using the same way of determining percentile chance of success ratiowise. I'm thinking skills will be learned by characters and come in two varieties: Physical and Spiritual. For every 2 Physical a character starts with, they learn 1 Physical skill. For every 2 Spiritual a character starts with, they learn 1 Spiritual skill. Physical skills include weapon use and any skill that relies on the physical. Spiritual skills include spells and any skill that relies on the mental. A character may use their full statistic when using a skill they have. Otherwise, the appropriate statistic will be divided in half or reduced to zero if the character is attempting a skill they do not know. Basically, if something is common, anybody can do it at full statistic... if something is uncommon, anybody can attempt it at half statistic... if something is rare, it cannot be attempted, as the statistic is reduced to zero for the unskilled.

So, there's a basic outline of the Universal Percentile System. Any feedback?

Additional stuff for the ratio/percentile system

Here are some additional rules I am working on for UPS:

If doubles come up during a percentile roll (same number for the ten and the one die), that will lead to a critical result. If the percentile roll failed with doubles rolled, that represents a critical failure. If the percentile roll succeeded with doubles rolled, that represents a critical success. That means that most anything can fail critically if double zeroes (00) are rolled, unless the chance for success is 100% (which would be represented by any percentile ratio where the opposing number is zero). It also means that the lowest percentile roll for critical success that can occur is double ones (11) being rolled, which would also mean that a percentile roll with a 10% or less chance of succeeding can succeed, but never critically succeed. I think that's apt for these rolls.
Should a critical success occur while attacking in combat, that would lead to double damage. Should a critical success occur while causing damage, that would lead to double the wound factors received. Critical failures would be the opposite, leading to attacks that backfire or weapons breaking while causing damage.

Weapon skills will cost two Physical skills, as opposed to a non-weapon Physical skill such as acrobatics or climbing that would cost the normal one Physical skill. By 'cost', I mean what is used up of the number of Physical skills alloted to a character.
Each type of weapon will have a bonus to Physical when used by those skilled in it; That bonus becomes a penalty if a weapon is used by a character that is not skilled in that weapon type. The damage weapons cause will be in increments of d10. This gives a random element to damage caused while still making sure weapons still remain deadly.

As far as damage goes, I'm think that Physical damage should cause wound factors, and Spiritual damage should cause trauma factors. Otherwise, the system would be limited in that the only damage a character or creature may incur is that of a physical nature, when psychological/spiritual damage should be factored in as well. Wound factors would lead to physical death, whereas trauma factors would lead to madness or loss of soul.

The basis for figuring out how powerful a creature, weapon, or other factor is within the ratio/percentile system will be that the average human's statistics will be Adroitness 11, Might 11, Intelligence 11, Will 11, Physical 22, Spiritual 22, Viability 22. Those statistics can be considered the opposing number when trying to figure out how something will relate to human standards. With this basis, I think it'll be pretty easy to make all sorts of characters, creatures, and items both large and small, no matter what the setting is.

That about covers it for now, but one thing I'll have to work on is experience. Characters should have a way to improve their statistics and learn new skills. I'll have to figure out if there's any sort of ratio/percentile way to figure out experience, or if it will just accrue the usual way... X amount of experience equals statistic gain or new skill learned.

Results Table

A number of war games use a "combat results table" (CRT) where you figure the ratio of attacker and defender power. For example, with Ogre and attack of 6 against a defense of 5 is rounded to 1:1, and thus you find on the table the set:

1 No effect
2 No effect
3 Damage
4 Damage
5 X Destroyed
6 X destroyed

Roll 1d6 and apply the outcome listed on the table. (With D's counting as no affect against Ogre components) At 2:1 attackers advantage, There are more Xs, at 1:2 there's only one X. Less than 1:2 or greater than 5:1 is no affect/instant kill respectively.

Perhaps, rather than needing to calculate the results, a CRT could be part of the character sheet or on the back cover of the book, so you just need a visual reference. A calculator is just one more step, and one more item on the table, which can be that much more distracting. especially when there are graphing calculators that can play games. (The TI-83 is common around here.)

Otherwise, it sounds like a decent idea, though I would like to know more about the setting of course.

You might want to edit your post to add some space between paragraphs to make it a little easier to read.

There is a fine line between hobby and obsession. I seem to have lost sight of it some time ago.

The CRT expanded

The CRT was used to great effect on a number of RPGs, and canbe a very simple tool. The best example of a CRT in RPGs was the one used on Advanced Marvel Super Heroes. The way this worked was simple.

The CRT was divided into a number of columns, one for each possible stat in the game (Shift 0 to Beyond). You then rolled the percentile dice and read across to see what colour of Feat (the outcomes were colour coded) you had achieved. Adjustments were made for the opposing characteristic - if any.

The CRT used in the Mayfair DC Heroes game was a bit more complicated, but more crunchy. The first table compared the two active characteristics in a task and gave a number that you needed to roll against to succeed. If you bettered the roll, you moved along the table counting the rows/columns to determine how many extra shifts you got on the next table.

Speaking of which, the next table compared the effecting characteristics to acch other (one damaging, one resisting). Agin, you cross referenced them and read off the final result, with shifts applied from the first table. This final result was the outcome of your task.

The advantage of the MSH version was that it was a one-roll system. However, it was not very fine-tuned. The DC system required a lot of finger pointing - unless you had the combat wheel or you memorised the formulae, like some of us grognards did.

CRTs do take the maths out of a situation, which may be worth the space they take up in a game.

Thanks for the input

I added spaces to the post to make it more readable. When I wrote it yesterday, I was in a rush and didn't have the chance to read over it.

As for a table showing the ratios, I pondered that but I thought it would just be easier to use a calculator. All calculations involved are simple, as it is all ratio based using the two factors of character's statistic versus opposing number. I hope to have a wide range of numbers, so having a chart to encompass them all seems superfluous when a calculator does the same trick. I actually like having the calculator be part of the game, as most RPGs don't do that. I could understand having reservations about calculator use becoming too overcomplicated for gameplay, but in this case the calculations will always be simple ratios that don't take much work to flesh out. I also think a calculator is useful for the core idea of the Universal Percentile System... that the game is percentile-based without using percentile-type statistics.

As for the setting, it's supposed to be a universal, generic system of using ratios and percentile probability as the main game mechanics for a RPG. As it were, though, I don't want to make it simple be a generic system, and would rather create the system then apply it to specific RPGs (to be created by me, most likely). For now, I have two ideas for setting: One was going to be Carnacki the Ghost Finder, but now that I see there's already a Carnacki RPG, I'll probably work on a generic horror/supernatural RPG called 'Mythos' that is sort of a fill-in-the-blanks version of Call of Cthulhu. The other idea I might use this system for is creating a RPG based upon 'The Stars My Destination', as that subject seems to have generated more interest than I initially expected.

I don't know when I'll get a chance to actually write a RPG using the Universal Percentile System (that's still a tentative title, by the way), as my laptop will soon be repaired and I have A LOT of 'B.L.O.G. #1 : Dimension Mansion' to write before I can even think of writing any other RPGs. Still, I was able to flesh out the percentile/ratio system using pen and paper while my laptop was out of commission, so I probably will complete it entirely once Dimension Mansion is finished.

Night Lands

I'll port it out to Night Lands if I can find the time. Since John mentioned it, I've been reading it. That way the Bill Hope Hodgson post will not be in vain.

Not in vain

The Carnacki post was well worth it in that it uncovered the Carnacki the Ghost Finder RPG (at least to me it did). I'm still going to make a supernatural horror game, but it'll be more Carnacki-ish than Carnacki.