From: jbridson@kean.ucs.mun.ca
Subject: RPG:  ARM version 1.1
Followup-To: rec.games.design
Organization: Memorial University. St.John's Nfld, Canada
Date: Sun, 24 Jan 1993 23:07:34 GMT

Okay, here is version 1.1 of the ARM system.  I give thanks to all the 
people who commented on 1.0.  I'm undecided over changing Fitness, so for 
the time being it stays.  Damage is slightly less lethal... More examples 
have been added.  The skill system has been changed, and the part on Scale 
was rewritten to (hopefully) make it less imposing.

    Robert Bridson (using jbridson's account)

---cut here---
                ARM:  Advanced Role-Playing Mechanics
                             version 1.1

                           by R. E. Bridson

                 Copyright 1993 Robert Edward Bridson

This document may be distributed freely and free of charge as long as 
the words are not changed, any additions are labelled as such, and no 
profit is made from the distribution.


Introduction..........................................................

ARM is an adaptable generic RPG, designed by a minimalist author.  
This means that details are often left up to the GM and the players - 
I prefer that room for my imagination to work, and I dislike getting 
bogged down in complex rules.  While there will be plenty of 
*guidelines* on how to manage things in later versions, this document 
contains all of the few rules.


                        SECTION 1:  THE RULES

Scale.................................................................

ARM uses a logarithmic scale for all its mechanics.  It is this scale 
which allows ARM to handle a huge variety of things, from the very 
small to the very big, while still using small numbers.  Also, it 
means that multiplication and division are almost completely absent 
from the system, while the effects of multiplying and dividing are 
still there!

How it works is that there are two sorts of values used.  One is 
called a measure value, which is a regular value that you can directly 
use.  The other is called a log value (log is short for logarithm).  
For every measure, there is a log.  Logs never have fractional parts 
or decimals, even though their corresponding measure might.

Whenever you add 5 to a log value, you are multiplying its measure by 
10.  Whenever you subtract 5 from a log value, you are dividing its 
measure by 10.

The following is a table to use in converting logs and measures back 
and forth.  It will only give you close approximates, but this is 
generally good enough for a game.

     Log  Measure        Log  Measure        Log  Measure
     -40  0.00000001                         10   100
     -35  0.0000001       0   1              15   1000
     -30  0.000001        1   1.5            20   10,000
     -25  0.00001         2   2.5            25   100,000
     -20  0.0001          3   4              30   1,000,000
     -15  0.001           4   6              35   10,000,000
     -10  0.01            5   10             40   100,000,000
     -5   0.1                                45   1,000,000,000

Now, if you know the log value and want to find its measure, you would 
follow these steps:

1.   Find the multiple of five that's closest to, but less than, your 
     log.  (eg. 10 would be the number to find for 10, 11, 12, 13, 14 
     and 15)  Call this number X.

2.   Look at your log again, and see how much bigger than X it is.  
     (eg. 16 is 1 greater than 15)  Call this number Y.

3.   Multiply the measures of X and Y together (both of which are 
     found on the chart)  The measure of X will only have a 1 and some 
     0's in it; the measure of Y will be 1, 1.5, 2.5, 4 or 6.

For example, say we wanted to know the measure of -3.  The closest 
multiple of 5 less than -3 is -5.  Looking that up on the chart, we 
get 0.1.  -3 is 2 greater than -5.  Looking 2 up on the chart we find 
2.5.  Multiply 0.1 and 2.5, we get a measure of 0.25 for the log value 
-3.

On the other hand, if you have a measure and want to find its log 
(approximately), you would follow these steps:

1.   Look at the first two digits of your measure (or first digit, if 
     it only has one).  Match them up with the closest pair of digits 
     in the middle column of the table (1, 1.5, 2.5, 4 or 6).  Find 
     the corresponding log, and call it X.

2.   Figure out in what place the first digit of your measure is (eg. 
     tens, hundreds, thousands, ones, tenths, etc...)  Match your 
     answer with the measures of multiples of 5.  Call the 
     corresponding log Y.

3.   Add X and Y together.  The sum is the approximate log of your 
     measure.

For example, to find the log of 1342, you would do this.  The first 
two digits, 13, are closest to 1.5.  Looking it up, we see 1.5 has a 
log of 1.  The first digit, the 1, is in the thousands place.  Looking 
up 1000 on the chart, we find a corresponding log of 15.  Adding the 
two logs together, we get 16 (15+1=16).  The log of 1342 is roughly 
16.

It is pretty simple, and you can quickly become so used to the numbers 
that you don't need the table any more.

[Note to the math-tolerant:  the scale is actually an approximation to 
a base 10^(1/5) logarithmic/exponential scale.  If you have a calcula-
tor capable of exponents and common logarithms, you can replace the 
steps above with calculator operations.  To find the log of measure A, 
enter <A> <Log> <*> <5> <=>, where <*> means the multiply button.  To 
find the measure of log B, enter <B> </> <5> <=> <10^x>, where </> 
means the divide button and <10^x> means the "10 raised to the 
exponent x" button.]



Stats.................................................................

There are six stats in ARM, common to almost all characters.  Note 
that ARM does not restrict you to using just these 6; some campaigns 
might require an additional stat (such as Magical Power).

     Fitness reflects agility, strength, reflexes, body coordination, 
     and so forth.  Most physical tasks are based on Fitness.

     Dexterity reflects a combination of manual coordination, hand-eye 
     coordination, lack of "shake" in the hands, nimble fingers, and 
     so on.  Most fine work is based on Dexterity.

     Toughness is a measure of stamina, endurance, hardiness, resi-
     stance to illness, etc...  Endurance tasks and withstanding 
     damage are usually based on Toughness.

     Wit reflects intellect, cognitive abilities, memory, observatio-
     nal skills, and so forth.  Mental problems are solved with Wit.

     Charisma represents the ability to interact with others.  Persua-
     sion, dominance, trickery, insults, leadership and haggling all 
     make use of Charisma.

     Willpower is self-explanatory.  Resisting pain, breaking addic-
     tions, staying true to your opinions, etc. are all tasks 
     involving this stat.

Each stat is assigned a log value.  For humans, an average log value 
would be 6 in each.  Humans almost always fit in the range 4-8, with 3 
and 9 being possible.



Situational Modifiers.................................................

While Stats form the basis of all actions, Situation Modifiers (Mods 
for short) can be added to stats to better simulate reality.  Mods are 
generally from -2 to +2, and apply to only certain situations or 
tasks.  Examples of Mods are "+1 Brawn", "+2 Empathic", "-1 Ugly".  If 
a character with +1 Brawn was in arm-wrestling, the +1 would be added 
to his Fitness log value for that action.  However, if the character 
was trying to dodge under an axe swing (an activity not relying on 
strength), the +1 would not be added.

There are also a few special mods.  For example, a small pixie is a 
lot more difficult to hit with a sword than a human.  However, that 
small pixie would not easily be noticed by a search party.  In one 
case, the small size benefits the character; in the other it does the 
opposite.  So, mods pertaining to size (among other things) are not 
given a + or - sign.  They are just given an absolute magnitude, that 
can be added or subtracted to a log value depending upon the 
situation.

Finally, some mods are special in that they grant the character an 
ability that others simply do not have.  For example, Flying +1.

Mods are often a key ingredient in defining a character.  For example, 
suppose we had a character with the following stats:

     4 Fitness      7 Wit
     8 Dexterity    5 Charisma
     6 Toughness    6 Willpower

These do not tell you much.  If you add +4 Musically Inclined, Perfect 
Pitch and -2 Weak Immune System, though, you begin to get a clear 
picture of a genius composer/musician who suffers from some childhood 
disease...



Skills................................................................

Skills are abilities in a specific area that characters pick up 
through experience.  They are very similar to mods, in that they each 
have a special value (usually from -3 to +3) that is added to a stat 
for activities involving the skill.  However, skills are usually both 
more specific in what activities they apply to, but are also broader 
in that a set of quite different activities (eg. waxing skis, and 
skiing down a slope) can be covered.  Also, characters normally have 
quite a few more skills than mods.

In a compendium of skills, there must be a description for each skill, 
in which there are listed several typical activities for it.  Each 
activity listed must say whether or not it can be done without the 
skill (and the accompanying penalty if this occurs), and a guideline 
as to what modifier you should place on that attempts - difficult 
tasks have penalties, easy tasks have bonuses.  Some activities will 
also have an accompanying table - more on this later.

Campaigns often do not require the level of detail given by some skill 
descriptions.  For example, a fast and humourous science-fiction 
campaign will probably not require any distinction between electronics 
engineering and civil engineering - all engineering skills could be 
handled as one broad group.  Skill compendiums generally break skills 
down into categories, such as "Engineering", "Music", "Combat" and so 
forth.  If your campaign doesn't require the given detail, put all the 
possible activities together into a broad skill by the name of the 
category.  You might need to exclude a few skills as separate from the 
category, however (eg. individual instrument types in the "Music" 
category).

What follows is a sample skill description.  There will be references 
to the next rule (Task Resolution).  Don't worry about these yet.  As 
you can see, a skill description can be quite in-depth.  This is to 
aid the GM, not to restrict or bog down the game.  If you find 
yourself continually leafing through a skill compendium searching for 
guidelines about an action, remind yourself that they're only 
guidelines and try to improvise more.

     Music Notation
     --------------
     Music Notation is the skill involved in the analysis, transcrip-
     tion and sight-reading of music.  It involves the knowledge of
     scales, modes, harmonies, non-harmonic tones, and so forth.  Wit 
     is normally the stat to use with Music Notation, with any musical 
     modifiers added (if appropriate).

     Difficulty:
     3  Simple piece (few modulations, simply rhythm, basic chords)
     6  Average piece (lengthy, variety of harmonies and rhythms)
     9  Tough piece (long, complex: eg. a full symphony)
     +2 Ancient piece (written before 1600's or so)
     -2 Partial analysis already given
     -3 Complete analysis already given

     Typical Activities:
     Analysis - Looking at sheet music to find things such as chords, 
     modulations, non-harmonic tones, and generally what the piece 
     sounds like.  Cannot be attempted without the skill.

          Result    Meaning
            -5      Complete misinterpretation, not realized.
          -4/-2     Mostly misinterpreted, know something is wrong.
           -1/0     Drew a blank for roughly half of the piece.
          +1/+4     Mostly interpreted correctly, a few blanks.
            +5      A perfect and complete analysis.

     Sight-reading - Playing music without prior memorization, just by 
     looking at the score.  Cannot be attempted without the skill.

          Result    Meaning
            -5      Simply could not read it.  Nothing played right.
          -4/-2     A few phrases done correctly, but mostly wrong.
           -1/0     Can recognize piece, but sounds awful.
          +1/+3     Performance mediocre at best (unless improvised)
          +4/+5     Excellent performance possible.
            +6      +1 or more on performance roll.

     Transcription - Copying music, possibly into a different key 
     (transposition).  The attempt can be attempted without training, 
     but with a -2 modifier.  

          Result    Meaning
            -5      The transcription is not recognizable.
          -4/-3     The transcription is mostly wrong, but the
                         attempter does realize this.
          -2/-1     The transcription is half wrong, but recognizable.
             0      Mostly right, several key mistakes though.
          +1/+2     Only minor errors.
            +3      Perfect transcription

     Note that Music Notation rolls should be made during composition 
     for both transcription and analysis.  However, both are easier 
     when it's your work; give a -2 modifier to the difficulty.



Task Resolution.......................................................

This is quite a simple mechanic.  First establish the difficulty 
number.  This may be assigned arbitrarily by the GM, according to this 
rough guide (assuming an average human is making the attempt):

     Trivial        1    (-5)
     Simple         4    (-2)
     50/50          6    
     Tough          8    (+2)
     Very Tough    11    (+5)

On the other hand, if the task is against something or someone else, 
the difficulty number will be decided differently.  The action that 
the other is using to compete with the first person is considered.  
The stat that is being used is taken with the appropriate situational 
mods added.  Then the GM may impose extra modifiers based on anything 
else (eg. weather, past injuries, cover, light level, drama).  If you 
are unsure of exactly what modifiers, you can use the modifiers in 
parentheses above as a guide.  Often skill descriptions will give a 
suggested difficulty number or modifier for the action, based on the 
expertise of the character.

Once the difficulty number is established, the character attempting 
the task takes the appropriate stat, adds any appropriate mods, and 
then makes a die roll.  They roll and add a d6, then roll and subtract 
another d6.  Henceforth this roll will be called d6-d6.

Now, the difficulty number is subtracted from this sum, to get the log 
of the "result" of the attempt.  As a general rule, a positive result 
means success, a negative result means failure, and a result of 0 
means either a draw or a marginal success/failure in favour of the 
character.  A result of +5 or more, or -5 and less is exceptional.

If the result is positive or 0, certain actions may call for 
additional calculations on the result.  These may include the addition 
of modifiers.  Occasionally, the result will be added as a modifier to 
another resolution.

Sometimes there will be a table to go with an action, on which you 
look up the final result.  Here it will tell more precisely what 
happens.  Often it involves converting to the measure of the result.



Movement Rates........................................................

Movement rates are based on a stat (in most cases, Fitness) with the 
appropriate mod added (if there is one).  However, a further modifier 
for the means of movement is added.  This further modifier is there to 
reflect that, for example, tunnelling is generally slower than 
sprinting.  For each possible and common form of movement for your 
character, you should record the combined stat+mod+further modifier.

Normally, a movement rate is the log value of the measure of the speed 
at which the character can move.  However sometimes this does not work 
(eg. in a near frictionless medium, such as space).  In these cases, 
the movement rate is the rate of acceleration, and finding speed takes 
a little more time.

Remember that the movement rate you calculate is the log value of the 
speed/acceleration.  When you actually move, you have to look it up on 
log chart to find the measure of how fast you are moving/accelerating.



Damage................................................................

Damage is decided with the task resolution mechanic described above.  
It is a contest of the quality of a blow against the character's 
Toughness.  The result is translated into wound and shock damage.  If 
the character is wearing some sort of protection, its Armour Value may 
be added to the character's Toughness (if the GM permits).

The level of wound damage is measured in six states:  Unharmed, Light, 
Moderate, Severe, Mortal, and Dead.  Wounds are also classified into 
these six states, and then added to the character's present wound 
level, by this table:

     Unharmed  =  0                Severe = 3
     Light     =  1                Mortal = 4
     Moderate  =  2                Dead   = 5

So a moderately wounded character (2) who took a severe wound (3) 
would be dead (2+3=5).

Damage from shock is divided up similarly, with six states:  Unharmed, 
Dazed, Giddy, Reeling, Fainting, and Unconscious.  They also corres-
pond to the numbers 0 to 5.  A dazed (1) character who took a giddy 
blow (2) would be Reeling (1+2=3).

Here is the damage table, where you can look up the result of a blow 
and find what wound and shock damage it did.

     Result    Wound          Shock
     --------------------------------------
       0       Unharmed 0     Dazed 1
       1       Light 1        Unharmed 0
       2       Light 1        Dazed 1
       3       Light 1        Giddy 2
       4       Moderate 2     Dazed 1
       5       Moderate 2     Reeling 3
       6       Severe 3       Giddy 2
       7       Severe 3       Fainting 4
       8       Mortal 4       Reeling 3
       9       Mortal 4       Unconscious 5
      10       Dead 5         Fainting 4
      11+      Dead 5         Unconscious 5
      16+           Destroyed.

If a certain type of blow is more of a stunning attack (eg. untrained 
punches), subtract one from the Wound damage and add one to the Shock 
Damage.  Sometimes, you may have to ignore one of the sorts of damage 
(eg. a mental attack that can't physically harm another person).

GM's are recommended to use imagination when dealing out wounds.  For 
example, that bear isn't just inflicted with a Light (1) wound, but is 
enraged when a burst-laser burns a small hole in its left ear.  Some 
GM's may even want characters to record exactly what their wounds are 
(and their is a maximum of five wounds per character).  Thus the 
shattered ankle you got from the fall might never heal properly...



Pushing...............................................................

If a character really needs a success, or a better result, they may 
elect to "push".  You can only push once per d6-d6 roll.  If you 
decide to push, you roll a third d6.  On a 1, nothing happens.  On a 
2-5, you get an extra +1 on the log value but your Shock damage is 
also increased one (from the exertion).  On a 6, you get the +1 to the 
log value, but at no cost in Shock Damage.

Pushing may also be used when moving.  Usually you wouldn't have to 
roll to move - you automatically go at the rate on your character 
sheet.  However, for each round you move, you can make a push roll (as 
above) to increase the log value of your movement rate.

Remember that it is the log value that you are adding 1 to.  It may 
not seem like much, but when you convert the result to real measures, 
the +1 is equivalent to adding 50% more effect!



Rounds................................................................

The word round was mentioned above; what exactly is a round?  It is a 
unit of time, decided by the GM.  It may be as short as a picosecond, 
or as long as a year, depending upon the circumstances.  Basically, it 
is how long it takes to complete the average action of the scene.  In 
a huge battle, the average action of deciding a skirmish might take 10 
minutes - making the round 10 minutes.  In an intense computer racing 
game, the average action of changing direction and moving might take 
only half a second - making the round worth half a second.

When an action sequence begins, the GM decides the length of the 
round.  Players then say what they're attempting to do that round, and 
the GM will decide what NPC's and the environment will do.  Attempts 
are resolved mechanic.  Values are updated, the GM decides if anything 
new happens, and then the next round starts.

Most games have rounds of only one standard length.  However, this is 
restrictive, as some situations obviously call for finer detail, or 
get boring because everything is happening too slowly.  So the game 
has to use and define more set units of time.  The effect usually is 
that there's a horde of different time-lengths to be learned, the 
system still is not as flexible as ARM, and players are tied to one 
units that they might not be happy with.

So ARM has no standard round length.  The bad part of being so 
flexible is that rates of movement, healing, and so forth must be 
converted to new units depending on the size of the round.  This means 
multiplication or division.  But ARM uses a  logarithmic scale - 
multiplying and dividing is equivalent to adding and subtracting logs.  
So to convert from a standard movement rate to something you can use 
for the current round length is a simple matter of chart look-ups and 
addition.  Some commonly converted units are listed on the following 
table:

     From ??? to standard               From standard to ???
     --------------------               --------------------
     kilometres...  +15                 kilometres...  -15
     metres...        0                 metres...        0
     centimetres... -10                 centimetres... +10
     millimetres... -15                 millimetres... +15
     inches...       -8                 inches...       +8
     feet...         -3                 feet...         +3
     miles...       +16                 miles...       -16

     seconds...       0                 seconds...       0
     minutes...      +9                 minutes...      -9
     hours...       +18                 hours...       -18
     days...        +25                 days...        -25
     weeks...       +29                 weeks...       -29
     years...       +37                 years...       -37

     * N.B.  If a speed is expressed in ??? per time unit, reverse the        
       sign of the translation (eg. to go from standard to ???/min,
       add 9).

     * N.B.  Both time units in an acceleration unit must be        
       converted.

Let's use examples to better illustrate the process of converting 
speeds and accelerations.

Corven is an assassin.  The log value of her sprint speed is 5.  
Converting to a measure, this means she can run at around 10 metres 
per second.  However, in a chase scene, the GM has decided that the 
round will be worth 3 seconds, and unfortunately the map they're using 
is in feet.

First of all, to convert from standard to feet means +3.  Adding +3 to 
her log value gives 8.  This means that the log value of her speed in 
feet per second is 8.

Next, we have to consider the round size.  It is in seconds, so we 
don't need to convert that.  However, we want to see how far she runs 
in 3 seconds, not 1 second.  Obviously, she can 3 times as far.  The 
log value of 3 is roughly 2.  So we add 2 to the previous result of 8, 
arriving at 10 for the log value of her speed in feet per 3 seconds.  
Converting this to a measure, we get her running at 100 feet every 
round.

Now, let's say that the starship Decius has a log value of 3 for its 
acceleration in space.  Standard acceleration is in metres per second 
per second.  However, the space map is at a scale of millions of 
kilometres.  Also, the GM has decided that the round size will be one 
hour on this journey.  So we need to convert the standard log value 
(in metres per second per second) to a log value in million Km's per 
hour per hour.

Converting from standard to kilometres is -15.  Subtracting 15 from 
the ship's value of 3 gives us -12.  Converting from kilometres to 
millions of kilometres means dividing by a million, or subtracting 30.  
We are now at -42.

Converting standard to hours is -18.  However, we are using per hours 
here, so we switch the sign to get +18.  We have to convert both "per 
hour"s, so we have to add +18 twice.

So the log value of the ship's acceleration in millions of Km's per 
hour per hour is -6 (-42+18+18=-6).  Converting to a real measure, we 
get 0.06.  Remember that this an acceleration value, so that we have 
to keep track of our speed separately.  If we want to accelerate for 
one round, we add 0.06 to our speed in millions of kilometres per 
hour.

Once you get the hang of it, it becomes quite simple.



Putting It All Together...............................................

Now you have all the basics of the ARM system.  However, this is not 
really enough to play with yet.  You probably want rules for resolving 
combat (both hand-to-hand, distance, and large-scale), using magic, 
driving vehicles, creating a character, and a host of other specific 
situations.  However, exactly how these are done depends upon personal 
taste for the most part, and there are many ways to do each of these.


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