fmitchell

FWIW, I started a thread a while back on golems and other constructs: http://basicroleplaying.com/showthread.php/1992-Golems-and-other-quot-constructs-quot-in-BRP-MRQ2 Warning: none of my stuff has been playtested.

I had similar concerns when representing golems, robots, androids, cyborgs, and the like, which are approximately man sized but denser than humans. I came up with a few solutions: Non-organic beings have split SIZ, one used for reach/height/volume and the other for weight/mass/force. (E.g. Strike Ranks would use Height SIZ, while Hit Points would use Mass SIZ. Damage bonus might use an average, given that the momentum of a fist depends both on mass and leverage.) See also the Density Control superpower. Tougher creatures may have more Armor Points, to represent the durability of a titanium frame or solid stone. Conversely, more fragile creatures might multiply damage from some or all sources, or like skeletons have a chance to shatter completely based on the amount of damage done. Armor might also differ based on the type of damage, e.g. a golem might blunt a cutting or impaling weapon (e.g. an axe), but succumb to a crushing weapon (e.g. a sledgehammer). Some creatures may take damage in odd ways, like creatures in Call of Cthulhu, e.g. Mi-Go take minimum damage from impaling weapons, shoggoths take only one point of damage from any kinetic weapon. GURPS has a more complicated damage system, which multiplies hit points that penetrate armor, and different multipliers for different types of creatures: living (most things), un-living (mainly robots and zombies), homogeneous (animated statues and the like), and diffuse (sapient swarm, water elemental). One need not go that far, but, for example, decreeing that zombies and golems take no extra damage from impales makes sense.

The Sorcery skill represents how much magical theory you know, and which level of common spells you can cast. Level 1 includes minor entropic effects like masking a private conversation with white noise. Level 5 includes summoning "weakly godlike" entities to destroy the world. One or more other skills determine whether you performed a casting correctly: Computer Use (Magic) for spells run on a computer, Science (Mathematics) for computations run by hand, the lower of Sorcery and an appropriate performance skill like Language (Aklo) or Knowledge (Occult) for old-school ceremonial magic, and a Difficult roll against Sorcery to run the spell in your own brain. (The last method also involves rolling to see how badly your brain gets fried.) If you fumble the casting roll (or merely fail performing Mental Magic), you roll on a fun Spell Failure Table. Note that spells cast from dedicated hardware, or well-tested software applications, always work. (Writes the man whose MacBook Pro crashed last night.) EDIT: All spells have a POW cost, but the POW comes from the casting technique, not the user. For example, a new laptop or desktop has POW 14, enough to comfortably run spells of Level 2 and below ... most simple effects. If the user need more power, there are ways to enhance the casting, some of them extremely unwise.

I'm just reading the Magic section now, but from my quick skim the power for spells comes from having the right ritual (or hardware/software) and enough time to perform the ritual (or run the computation). In the Laundryverse, magic comes from specific types of mathematical computations, which resonate across the multiverse and open a gate between our universe and some other, far stranger one. Information goes in, and energy that creates the magical effect comes out ... or possibly a brain-eating horror from Beyond, depending on the spell and how badly you screwed up.

Available from DriveThruRPG.com: http://rpg.drivethrustuff.com/product_info.php?products_id=54233

(Apologies for table formatting: even with CODE tags, formatting is too difficult.) Golems are animated clay statues approximately 2m high, constructed through magical or alchemical means. After constructing the statue to very exacting specifications, its builder gives it pseudo-life through a scroll placed in its head. Removing the scroll deactivates the golem. (Some makers place the scroll in the chest. Some variations inscribe holy words or symbols somewhere on its body.) Golems lack CON, POW, and CHA; HP are based on 2 * SIZ. Golems are immune to all effects resisted by Persistence or Resilience, and all forms of mind control. They have an INT score, reflecting their ability to understand speech and perform menial tasks, but golems can only follow directions. Since they never need food and never tire, they make ideal guards, laborers, or warriors. Golems are never stunned, distracted, or incapacitated by wounds to the limbs, chest, or abdomen. Being solid clay, no Combat Maneuver can increase damage against it. A Major Wound automatically destroys the location, but the golem suffers no other effects: it can continue on without a lower body, and sometimes without a head. Only destroying its scroll or inscription stops it. STR: 35 SIZ: 20 INT: 8 DEX: 10 Combat Actions: 2 Damage Modifier: +1D12 Movement: 6m Strike Rank: 13 D20 | Locations | AP/HP 1-3 | R. Leg | 6/8 4-6 | L. Leg | 6/8 7-9 | Abdomen | 6/9 10-12 | Chest | 6/10 13-15 | R. Arm | 6/7 16-18 | L. Arm | 6/7 19-20 | Head | 6/8 Typical Armor: Solid clay (AP 6), no penalties Traits: Dark Sight (no penalties), Formidable Natural Weapons, Homogeneous, Unliving Skills: Athletics 35%, Brawn 125%, Evade 16%, Perception 75%, Persistence n/a, Resilience n/a, Unarmed 75% Homogenous: Creature has no joints, organs, blood, or other vulnerable parts. The following Combat Maneuvers have no effect: Bleed, Bypass Armor (against its natural AP), Impale, Maximize Damage, and Sunder (against its natural AP). Unliving: Creature is immune to poison, disease, and fatigue. It does not need to breathe, eat, or sleep. It cannot heal on its own, and healing spells do not work; a Repair spell or a successful Craft test will repair damage. Weapons Type, Size, Reach, Weapon Skill, Damage, AP/HP Fist, S, T, 75%, 1D6+1D12, as for Arm Great sword, H, L, 50%, 2D8+1D12, 6/12 Great club, H, L, 50%, 2D6+1D12, 4/10 Great axe, H, L, 50%, 2D12+2, 4/10 Variations Other Sizes: STR, SIZ, and related attributes for clay golems of other sizes are given below. Height | 1m | 3m | 4m | 6m STR | 25 | 45 | 60 | 80 SIZ | 10 | 35 | 50 | 80 Damage Modifier | +1D4 | +2D6 | +2D10 | +3D8 Movement | 4m | 8m | 10m | 12m Strike Rank | 10 | 18 | 23 | 33 Adjusted HP per Location | -4 | +6 | +12 | +24 Materials other than Clay: Other materials are more or less dense than clay. The following chart provides adjustments to the statistics above: Armor Points, Movement, and a multiplier for SIZ. Calculate the Damage Modifier based on the new SIZ, but do not change the Strike Rank: the golem has changed mass, but not reach. Material | AP | SIZ Multiplier | Movement ----------------------------------------------------- Bronze | 12 | x 3 | 6m Iron | 12 | x 3 | 4m Gold | 4 | x 3 | 4m Stone | 10 | x 2 | 4m Wood & Metal | 4 | x 1 | 8m Sapient Golems: INT becomes 2D6+6, DEX 3D6. If magically active, add POW 3D6. Humanlike Golems: add CHA 3D6 and sapience (see above), and the golem can impersonate a human to some degree (perhaps with concealing clothing and a disguise). Specialized Golems: Some golems, especially sapient golems, might be built for specific tasks. For example: Companion: meant to "entertain" humans, generally given a female form. Humanlike and Sapient (see above), usually Wood and Metal construction, with SIZ 10, STR 12, and DEX 15. Advisor: advisor to rich and powerful, something like a walking computer. Sapient (see above), Medium, any construction, with INT 3D6+6. Some might build only a talking Brass Head: bronze construction, SIZ 10, no STR or DEX (use INT alone to determine Strike Rank), INT 2D6+12. Warrior: Specialized for combat. Use any base model, but increase DEX to 14. Some warrior models have been known to go berserk.

(The thread's eyes glow red, and a stainless steel skeleton climbs from the wreckage ...) Sorry to necro this thread, but there's one more issue I'm fiddling with, especially with regards to high-tech constructs: how do I model a human-sized android that's more resilient -- and more dense -- than a human of the same size: Use a CON score, just like everything else. Duh. Set SIZ based on the comparable human, and give it extra armor to reflect its more durable structure. Set SIZ based on mass, with a note on actual dimensions Use a split SIZ for height/mass: the Height SIZ determines Strike Rank (if used), and the Mass SIZ determines Hit Points and Strength Bonus. I favor option #4, maybe combined with #2. I'd prefer to add as few new rules as possible, to avoid confusing GMs and players alike. However, I might need different rules for different situations, e.g. golems made of solid stone or clay vs. technological androids made of titanium, plastic, carbon fiber, and more exotic materials.

I'm fiddling with porting other magic systems to BRP / MRQ2. (And BRP systems to MRQ2, which is much easier.) I haven't gotten far, but my queue includes: Barbarians of Lemuria Sorcery Book/Path Magic (GURPS Thaumatology) Genius: the Transgression Mad Science Incantations (d20) Mage: the Awakening Magic Miracles (All Flesh Must Be Eaten) S. John Ross's Hedge Magic (GURPS, FUDGE, etc.) True20 Powers In some cases, I'm combining similar systems for a "best of breed" in BRP, e.g. my Incantations system also borrows from Occultism from A Magical Medley (FUDGE), Magic from Buffy and Ghosts of Albion (Unisystem), Castle Falkenstein Sorcery, and a little bit of Call of Cthulhu Magic.

What are the differences? (I already bought Sailing on the Seas of Fate, and RQ3 is currently in storage.)

Your armor/damage system sounds a lot like a variant in Unearthed Arcana, later refined in Mutants & Masterminds and True20: one roll to hit, another "saving throw vs. damage" with armor adding to the second roll. (If it helps, the "soak roll" is older than 3.x.)

I'm not as keen; I'd rather have two separate values. Armor Points represent how hard it is to crack stone (clay, iron, whatever), whereas Hit Points represent how much stone you have to crack. They aren't correlated. As I mentioned above, I looked up the AP and HP of a boulder in the MRQ2 main book, since from a purely mechanical perspective it's an inanimate object. Then I guessed at the AP of Bronze, Iron, and Clay. Different sizes of golems have different HP, but the same AP. Maybe I should just post my working draft for Golems ... and Synthetics, my term for high tech robots, artificial intelligences, and full-body cyborgs.

Sorry, which ship rules? I don't see any in the Gold Book or MRQ2, and I don't have any Stormbringer material. Having said that, I looked at the Mongoose Traveller rules for ships, drones, and robots. However, I don't like adding a whole new subsystem for golem (or even robot) combat, so I'll just use regular damage and hit locations. A few special rules, or rather rule exemptions: Golems don't stop if they take Serious or Major wounds, although once they hit 0 HP, they're gone. (If using hit locations, -HP in that location means it shatters or falls off automatically. Unless it's the head or chest, though, it will only slow them down.) Golems are not only clay (or stone, or metal), they're solid clay (etc.), so criticals and specials do no extra damage. In MRQ2, certain combat maneuvers just don't work (e.g. Bleed, Bypass Armor against its natural armor, Impale). Because they're solid, they have high AP. Clay golems have 6 AP, while Bronze/Iron golems have 12 AP and Stone Golems have 10 AP (based on the armor value of a boulder given on page 63 of MRQ2). Damaging a golem requires big blunt instruments like a war hammer; swords will lose their edge and arrows bounce off. BTW, to explain some of my design choices: I started with Skeletons in BRP, which have no CON and only token POW. (Curiously, robots in a later section have the full complement of characteristics, although the description states that POW is an internal energy source, not spiritual power. The "Figure of Earth" was really a special kind of Earth Elemental. I was aiming more for a robot created by magic (or alien technology, in some cases).

Well, it's a function of density, anyway. Maybe I should start with the SIZ of a Ballistic Gel Golem, then multiply by the density of various materials. (I'm not sure how STR or DEX should change. Perhaps STR scales by the same factor, and DEX is inversely proportional to density?) Normally, yes, but since I've decided Constructs have no CON, I'll have to use SIZ for total HP, or SIZ*2 for hit location HP lookup in MRQ2. If I base SIZ on weight, though, that makes more sense ... although there may be cases where the rules assume SIZ is proportional to volume, e.g. how easy a target is to hit. Maybe I should keep SIZ as it is, with a note that knockback and other mass-related rules should use original HP instead. Technological constructs aren't homogeneous, so I'll just use a constant factor to represent the average density of hydraulics, ceramics, steel, silicon, carbon fiber, and various forms of unobtainium. I'll also double-check the Gold Book for any additional advice on robots.

Mostly for my own amusement, I'm throwing together some rules for golems and other constructed creatures in BRP, MRQ, and other d100-based games. So far I'm working on the following principles: Constructs do not have CON. Hit Points are determined using SIZ only, (SIZ + STR)/2, whichever is higher (to reflect that stronger constructs are generally denser), or a multiple based on construction materials. Constructs that can only follow orders have Fixed INT, like animals, albeit in the 8-12 range, and no APP (or CHA in MRQ2). Sapient constructs have regular INT, and (usually low) APP/CHA to gauge social aptitude. Constructs lack POW, unless they have "souls" or a presence on the Spirit Plane. Magical effects have a zero Power Point cost, use points from a built-in "battery" (similar to the ones in Equipment), or else have another limitation like "Always On" or charges. Constructs generally require no food, sleep, or air, and are immune to poisons and diseases. Technological constructs have optional rules for running on batteries. Constructs take Serious and Major Wounds without being stunned, distracted, or incapacitated. On the other hand, at HP 0 they cease functioning. If using hit locations, reaching -HP in an area automatically disables/destroys the limb hit. Disabling a construct's head does not necessarily destroy a construct unless it slices through a Golem's chem or a cyborg's brain; it will probably blind the construct, though. Destroying the chest, on the other hand, will destroy a construct, and abdomen hits will destroy a technological construct's power system. Golems, for example, have standard sizes which determine STR and SIZ. (DEX and INT are the same for all golems.) Armor points and hit points (as a multiple of SIZ) depend on the golem's construction: clay, stone, iron, bronze, wood on a metal armature, etc. For BRP SF and MRQ2 expeditions to barrier peaks, high tech androids and robots determine hit points from the greater of SIZ and (SIZ + STR)/2. Armor Points, STR, SIZ, INT, and DEX for non-sapient robots are fixed values based on the robot's intended purpose, while sapient "synthetic people" have randomly-determined stats and an CHA/APP score. (Full body replacement cyborgs, having one organic component, resemble sapient androids except that the brain has a low CON or Resilience used only when biological agents penetrate its life support system.) However, I'm pondering a few open questions: A man-sized stone figure ways way more than a man would. Should I base SIZ on physical dimensions or weight? Should Constructs just have dimensions and weight directly instead of size, like Elementals do? If so, how would I determine a Damage Bonus? Should I involve STR in HP calculation at all? Should Golem STR and DEX also vary by construction materials? (An old GURPS article does just that, with characteristically exhaustive lists of every possible material, from Adamant and Aluminum to PVC and Wool.) How should I scale STR generally? One document in the Downloads section gives Bronze Golems a STR of 25+/-4, while stats for a Terminator in another document use a STR of 60 to 100. (Generally, I want a single Golem to be a challenge to a group of PCs, and robots to have "sensible" scores based on SIZ and purpose. Artificial people and FBR Cyborgs, in particular, should be suitable for PCs in a high-powered high tech game.) Should golems, especially, have extra rules because they're made of solid material rather than fiddly technical parts? (The aforementioned Bronze Golems in the Downloads section downgrade all successes by one level, instead of having AP.) Does everything else above sound all right?

I'd make a particular magical tradition or domain a skill, and base success or failure of your "plausible deniability" magic depend on it. E.g. you might have skills for Healing, Passion, Nature, Curses (on a person), Blessings (on a person), etc. For comparison, GURPS Thaumatology details a "Book/Path" system for ritual magic, in which magical skills cover logically related effects ("Paths"), or arbitrary but pre-defined powers learned from a book or tradition. Since it's a little more functional, the options for game balance are Effect Shaping (a penalty to the roll based on power/complexity of the effect) and Energy Accumulation (repeated rolls to gather "power", the amount of which depends on the desired effect). One idea I've seen for other systems is to use social manipulation (Persuade, maybe with Sleight of Hand) to achieve the effect of a "curse" or "blessing". Success means that the subject believed your mumbo-jumbo, and gets bonuses or penalties to skills. Note that Fake Magic won't work on inanimate objects, animals, or even other people who don't share your belief system. Another random idea, based on the Polynesian concept of mana, is that every time you succeed at a task, your Mana goes up, while Fumbles or humiliating failures make it go down. Mechanically, one could use Allegiance to represent a character's Mana, except that the score will go down if it's invoked and fails, the character fumbles, or the character suffers a humiliating defeat through bad luck or bad planning.

I'd treat "sleeves" as equipment, limited by the character's credit rating, and use a sort-of point buy to determine the cost of a sleeve. Perhaps that just postpones the problem. Anything that sticks with the character I'd treat as a straight skill: Sensor Use, Gravitic Steering, etc. I'd imagine, even with integrated circuitry, a mind needs to practice using particular sensors, manipulators, and motors to get the most out of them.

I think I'm there, or at least close enough for government; error is < 1.5%. This after a whole bunch of screwed up algebra, geometric arguments, and triple-checking my work. I also refactored the numerical procedure, to reduce duplication and to mirror the rules more closely. Here's the full program: #!/usr/bin/env ruby require 'rational' STEP = 10 LEVEL_CRIT = 3 LEVEL_SUCC = 1 LEVEL_FAIL = 0 LEVEL_FUMB = -1 # # Categorize a roll as a critical success, regular success, # failure, or fumble. # # pct - percentile skill, 1...99 # roll - actual roll of resisting skill, 1...99 # # returns LEVEL_CRIT, LEVEL_SUCC, LEVEL_FAIL, LEVEL_FUMB # def success_level(pct, roll) pct_crit = (0.10 * pct).ceil # critical value if (roll == 100) or (roll == 99 and pct >= 100) then return LEVEL_FUMB elsif roll > pct then return LEVEL_FAIL elsif roll > pct_crit then return LEVEL_SUCC else return LEVEL_CRIT end end # # Determine the probability of success in an opposed skill test # through brute-force counting. # # pct_a - percentile value of active skill, 1...99 # pct_r - percentile value of resisting skill, 1...99 # # returns Rational with value between 0 and 1. # def opposed_prob_count(pct_a, pct_r) success = 0 # Enumerate all possible rolls of two d100 1.upto(100) do | roll_a | 1.upto(100) do | roll_r | # compare success levels level_a = success_level(pct_a, roll_a) level_r = success_level(pct_r, roll_r) if level_a > LEVEL_FAIL then if level_a > level_r then success += 1 elsif level_a == level_r then # compare die rolls if (roll_a > roll_r) then success += 1 elsif (roll_a == roll_r) and (pct_a > pct_r) then success += 1 end end end # If active fails or fumbles, never a success end end return Rational(success, 10000) end # # Determine the probability of success in an opposed skill test # mathematically. # # pct_a - percentile value of active skill, 1...99 # pct_r - percentile value of resisting skill, 1...99 # # returns Rational with value between 0 and 1. # def opposed_prob_math(pct_a, pct_r) prob_a = Rational(pct_a, 100) prob_r = Rational(pct_r, 100) # Clear successes: crit vs. non-crit, success vs. failure result = prob_a - Rational(91, 100) * prob_r * prob_a # Successes based on one die roll over another if pct_a <= pct_r then result += (101 * prob_a * prob_a + prob_r * prob_r - 20 * prob_a * prob_r) / 200 else result += prob_a * prob_r * 82 / 100 - \ (101 * prob_r * prob_r + prob_a * prob_a - 20 * prob_r * prob_a) / 200 end return result end puts("Active/Resisting\n") printf("%2s ", "") 1.upto(100/STEP - 1) do |r| printf("%2s%2d%2s ", '', r * STEP, '') end puts("\n") 1.upto(100/STEP - 1) do |a| pct_a = a * STEP printf("%2d ", pct_a) 1.upto(100/STEP - 1) do |r| pct_r = r * STEP printf("%6.3f ", opposed_prob_math(pct_a, pct_r) * 100) end puts("\n") printf("%2s|", '') 1.upto(100/STEP - 1) do |r| pct_r = r * STEP math = opposed_prob_math(pct_a, pct_r) count = opposed_prob_count(pct_a, pct_r) printf("%6.3f|", ((count - math)/count) * 100) end puts("\n") end

Last night I noticed that the Ruby program to generate probabilities with brute-force counting accidentally counted cases in which the Active roll was a success and the Resisting roll was a critical. I feel like an idiot. On the other hand, maybe that's why they were higher than the formula I worked out. At any rate, I've corrected the problem and refactored the program to represent the rules more directly. I think I've also derived a workable equation, but I'll have to test it first. FWIW, here are the corrected probabilities: Active/Resisting 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 5 4.850 4.650 4.410 4.210 3.980 3.780 3.560 3.360 3.150 2.950 2.740 2.540 2.330 2.130 1.920 1.720 1.510 1.310 1.100 10 9.850 9.450 8.910 8.460 7.930 7.480 6.960 6.510 6.000 5.550 5.050 4.600 4.110 3.660 3.180 2.730 2.260 1.810 1.350 15 14.840 14.590 13.800 13.150 12.360 11.710 10.930 10.280 9.510 8.860 8.100 7.450 6.700 6.050 5.310 4.660 3.930 3.280 2.560 20 19.790 19.540 18.850 17.900 16.810 15.910 14.830 13.930 12.860 11.960 10.900 10.000 8.950 8.050 7.010 6.110 5.080 4.180 3.160 25 24.770 24.570 23.890 23.190 21.750 20.650 19.310 18.210 16.880 15.780 14.460 13.360 12.050 10.950 9.650 8.550 7.260 6.160 4.880 30 29.720 29.520 28.790 28.090 26.850 25.350 23.710 22.360 20.730 19.380 17.760 16.410 14.800 13.450 11.850 10.500 8.910 7.560 5.980 35 34.690 34.540 33.820 33.170 31.940 30.790 28.700 27.150 25.260 23.710 21.830 20.280 18.410 16.860 15.000 13.450 11.600 10.050 8.210 40 39.640 39.490 38.720 38.070 36.790 35.640 33.850 31.800 29.610 27.810 25.630 23.830 21.660 19.860 17.700 15.900 13.750 11.950 9.810 45 44.600 44.500 43.740 43.140 41.870 40.770 38.990 37.390 34.650 32.650 30.210 28.210 25.780 23.780 21.360 19.360 16.950 14.950 12.550 50 49.550 49.450 48.640 48.040 46.720 45.620 43.790 42.190 39.850 37.250 34.510 32.260 29.530 27.280 24.560 22.310 19.600 17.350 14.650 55 54.510 54.450 53.650 53.100 51.790 50.740 48.920 47.370 45.040 42.990 39.600 37.150 34.160 31.710 28.730 26.280 23.310 20.860 17.900 60 59.460 59.400 58.550 58.000 56.640 55.590 53.720 52.170 49.790 47.740 44.850 41.700 38.410 35.710 32.430 29.730 26.460 23.760 20.500 65 64.420 64.390 63.550 63.050 61.700 60.700 58.840 57.340 54.970 52.970 50.090 47.590 43.550 40.650 37.110 34.210 30.680 27.780 24.260 70 69.370 69.340 68.450 67.950 66.550 65.550 63.640 62.140 59.720 57.720 54.790 52.290 48.850 45.150 41.310 38.160 34.330 31.180 27.360 75 74.330 74.320 73.440 72.990 71.600 70.650 68.750 67.300 64.890 62.940 60.020 57.570 54.140 51.190 46.500 43.150 39.060 35.710 31.630 80 79.280 79.270 78.340 77.890 76.450 75.500 73.550 72.100 69.640 67.690 64.720 62.270 58.790 55.840 51.850 47.600 43.210 39.610 35.230 85 84.240 84.240 83.320 82.920 81.490 80.590 78.650 77.250 74.800 72.900 69.940 67.540 64.070 61.170 57.190 53.790 48.450 44.650 40.010 90 89.190 89.190 88.220 87.820 86.340 85.440 83.450 82.050 79.550 77.650 74.640 72.240 68.720 65.820 61.790 58.390 53.850 49.050 44.110 95 94.150 94.150 93.190 92.840 91.370 90.520 88.540 87.190 84.700 82.850 79.850 77.500 73.990 71.140 67.120 63.770 59.240 55.390 49.400

Yeah, that's why those cases aren't included. The cases in red, above, are mutual FAILURES. Not successes. I noticed that too; nothing in the MRQ2 Core Book. However, the errata say "If a draw is rolled in an Opposed Test (both participants rolls exactly the same dice result and Level of Success) then the character with the highest score in the skill is considered the winner." I simply considered all ties as failures. (And what if both characters have exactly the same skill level?)

Oh, here's the Ruby code that I used to generate the table, in case I made a mistake there: #!/usr/bin/env ruby require 'rational' # # Determine the probability of success in an opposed skill test # through brute-force counting. # # pct_a - percentile value of active skill, 1...99 # pct_r - percentile value of resisting skill, 1...99 # def opposed_prob(pct_a, pct_r) pct_a_crit = (0.10 * pct_a).ceil # critical for pct_a pct_r_crit = (0.10 * pct_r).ceil # critical for pct_r success = 0 # Enumerate all possible rolls of two d100 1.upto(100) do | roll_a | 1.upto(100) do | roll_r | # count successful combinations if roll_a <= pct_a_crit then if roll_r > pct_r_crit then # Active rolled critical, resisting didn't success += 1 elsif roll_a > roll_r then # Both criticals, active rolled higher success += 1 end elsif roll_a <= pct_a then if roll_r > pct_r then # Active rolled success, resisting didn't success += 1 elsif roll_a > roll_r # Both successes, active rolled higher success += 1 end end # Active failed or fumbled => no success end end return Rational(success, 10000) end puts("Active/Resisting\n") printf("%2s ", "") 1.upto(19) do |r| printf("%2s%2d%2s ", '', r * 5, '') end puts("\n") 1.upto(19) do |a| pct_a = a * 5 printf("%2d ", pct_a) 1.upto(19) do |r| pct_r = r * 5 printf("%6.3f ", opposed_prob(pct_a, pct_r) * 100) end puts("\n") end

I'm trying to account for double-counting -- (P[a] - P[a]/10), not (P[a]) -- but I'm probably missing something. (Then again, my candidate formulas have been coming in too low, so maybe I'm undercounting, or rounding down when I should go up.) The verbal algorithm uses "or else" to indicate if one clause is true, then the others aren't considered. Unfortunately math doesn't work that way. I'm only counting cases where the active player succeeds, to get a total success probability. If the active player fails or fumbles, then by definition he doesn't succeed. (Even if the resisting roll fumbles, a failure is a failure.) Computing the chance of failure is an exercise for the reader.

My probability-fu is weak. I tried to derive a formula to calculate the probability of success (by whatever margin) in opposed percentile rolls: the active roll is a critical and the resisting roll is not a critical, or else the active roll is a regular success and the resisting roll is a failure, or else both rolls are critical successes and the active roll is higher than the resisting roll, or else both rolls are regular successes and the active roll is higher than the resisting roll, So, using the MRQ2 definition of critical success (1/10 of skill, rounded up), I get: Success = (P[a]/10)*(1-P[r]/10) + (P[a] - P[a]/10)*(1-P[r]) + Q(crit) + Q(reg) where P[x] is the percentage for x, "a" is the Active roll, and "r" is the Resisting roll. Q(y) is the factor for the case where the active roll is greater than the resisting roll, and needs to be broken into two parts: the critical vs. critical case and the regular vs. regular case. Unfortunately, when I try to express both values of Q, I keep getting different results however I derive it. (It's partly algebraic mistakes, I think.) When I do get a formula, I try match it to results I derived numerically (enumerate all possible active rolls and resisting rolls, and count all cases that denote a success). FWIW, here are the numerical results I obtained, in increments of five: Active/Resisting 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 5 4.890 4.690 4.480 4.280 4.070 3.870 3.660 3.460 3.250 3.050 2.840 2.640 2.430 2.230 2.020 1.820 1.610 1.410 1.200 10 9.890 9.540 9.080 8.630 8.170 7.720 7.260 6.810 6.350 5.900 5.440 4.990 4.530 4.080 3.620 3.170 2.710 2.260 1.800 15 14.930 14.630 14.060 13.410 12.740 12.090 11.420 10.770 10.100 9.450 8.780 8.130 7.460 6.810 6.140 5.490 4.820 4.170 3.500 20 19.930 19.630 19.060 18.260 17.340 16.440 15.520 14.620 13.700 12.800 11.880 10.980 10.060 9.160 8.240 7.340 6.420 5.520 4.600 25 24.960 24.710 24.190 23.440 22.410 21.310 20.180 19.080 17.950 16.850 15.720 14.620 13.490 12.390 11.260 10.160 9.030 7.930 6.800 30 29.960 29.710 29.190 28.440 27.410 26.160 24.780 23.430 22.050 20.700 19.320 17.970 16.590 15.240 13.860 12.510 11.130 9.780 8.400 35 34.980 34.780 34.310 33.610 32.630 31.430 29.940 28.390 26.800 25.250 23.660 22.110 20.520 18.970 17.380 15.830 14.240 12.690 11.100 40 39.980 39.780 39.310 38.610 37.630 36.430 34.940 33.240 31.400 29.600 27.760 25.960 24.120 22.320 20.480 18.680 16.840 15.040 13.200 45 44.990 44.840 44.420 43.770 42.840 41.690 40.250 38.600 36.650 34.650 32.600 30.600 28.550 26.550 24.500 22.500 20.450 18.450 16.400 50 49.990 49.840 49.420 48.770 47.840 46.690 45.250 43.600 41.650 39.500 37.200 34.950 32.650 30.400 28.100 25.850 23.550 21.300 19.000 55 54.990 54.890 54.520 53.920 53.040 51.940 50.550 48.950 47.050 44.950 42.540 40.090 37.580 35.130 32.620 30.170 27.660 25.210 22.700 60 59.990 59.890 59.520 58.920 58.040 56.940 55.550 53.950 52.050 49.950 47.540 44.940 42.180 39.480 36.720 34.020 31.260 28.560 25.800 65 64.990 64.930 64.610 64.060 63.230 62.180 60.840 59.290 57.440 55.390 53.030 50.480 47.610 44.710 41.740 38.840 35.870 32.970 30.000 70 69.990 69.930 69.610 69.060 68.230 67.180 65.840 64.290 62.440 60.390 58.030 55.480 52.610 49.560 46.340 43.190 39.970 36.820 33.600 75 74.990 74.960 74.690 74.190 73.410 72.410 71.120 69.620 67.820 65.820 63.510 61.010 58.190 55.190 51.860 48.510 45.080 41.730 38.300 80 79.990 79.960 79.690 79.190 78.410 77.410 76.120 74.620 72.820 70.820 68.510 66.010 63.190 60.190 56.860 53.360 49.680 46.080 42.400 85 84.990 84.980 84.760 84.310 83.580 82.630 81.390 79.940 78.190 76.240 73.980 71.530 68.760 65.810 62.530 59.080 55.290 51.490 47.600 90 89.990 89.980 89.760 89.310 88.580 87.630 86.390 84.940 83.190 81.240 78.980 76.530 73.760 70.810 67.530 64.080 60.290 56.340 52.200 95 94.990 94.990 94.820 94.420 93.740 92.840 91.650 90.250 88.550 86.650 84.440 82.040 79.320 76.420 73.190 69.790 66.050 62.150 57.900 Help?

Which PDFs did you get? So far, I just have Harn World 2nd edition: maps, atlas, cosmology, glossary. I'm just planning to change the fluff as I see fit; my version won't have elves, dwarVes, and orcs, merely forest-folk, hill-folk, and barbarians. I've thought about getting some of the deeper background, but most of it smelled too D&D-ish: wizards, priests, the aforementioned demi-humans. Then again, I haven't dived too deeply into the Harn World text, so perhaps I'll have to change more than I think. To answer your question ... I would change the setting to fit the system you've chosen. For example, the Great Spells of yore are lost. Sorcery has split into hundreds of smaller, squabbling orders trying to preserve what they have left. Priests beseech their gods for greater powers, but the gods do not reply. Even shamans, who have preserved the past, noticed that the great spirits have hidden themselves away, and lesser ones have become wilder ... That's sort of the idea of my quasi-Harn campaign: the old powers are fading, and new ones are arising. The new powers use systems from BRP, Corum, and Unknown Armies, with large chunks of handwavium: allegiances, demon-summoning, new sciences, avatars of folkloric archetypes. As an alternative, I'm hacking out a ritual magic system, to explain great magics of the past. I'm either going to use multiple rolls on the ritual casting skill (modeled after d20 Incantations), or opposed rolls against a "resistance factor" (nature fighting back, eldritch powers refusing mortal commands, etc.). A simple difficulty factor might also work, although I like the nonlinear effects of opposed and multiple skill checks.

This is cool, thanks. I'd imagine it would also be useful in developing new humanoid creatures smaller than an average human. One question, though: was the data only for American children? All Caucasians? Average of all races? Adult heights and weights vary by region and time period; for example, according to one source, modern Japanese are shorter than Americans by 10.16 cm

Unless you have Basic Magic or RuneQuest 3 (Avalon Hill/Chaosium). For that matter, the "Magic" system is a prototype of RQ Sorcery, and "Sorcery" is someone analogous to RQ2 Battle Magic / RQ3 Spirit Magic / MRQ2 Common Magic.