The primary need for mechanics in a roleplaying game is to permit fair ajudication of conflicts and their consequences. Definition of the characters and the world they exist in is subsidiary to this: if there were no conflict, there would be no need to define characters' capabilities.
When considered abstractly enough, any action, even one that seems to be unopposed, can be cast as a conflict, either between two (groups of) characters or between a character (or group) and the world. Thus, a mechanism for resolving conflicts generalizes to all necessary game mechanics. That's my story, and I'm sticking to it.
Presented here is a simple system for quickly resolving fights, physical contests, intellectual puzzles, internal or external emotional struggles, or any other sort of conflict. Because it is simple, and because it applies to all types of conflicts and therefore is quite abstract, considerable interpretation will be required by the GM and players to produce color commentary and details of the horrible fates befalling the characters: the description of the results will only be as good as the description of the action undertaken.
A character's ability in any given field of endeavor is expressed as a number. Depending on the style of the game and character of the players, a character may have ratings in a few broad abilities, many narrow abilities, a few narrow abilities with all others being at a default value, or some combination or intermediate, but what's important is that a number can be assigned. The actual number doesn't matter; for most purposes it is the ratio of the ratings of the challengers that determines the result, so a challenge between a rating of 7 and a rating of 9, a rating of 14 and a rating of 18, or a rating of 70 and a rating of 90 would all turn out the same way.
Inanimate objects, forces, phenomena, or situations are also rated with respect to what characters are likely to try to do despite them: climb a cliff, lift a boulder, pick a lock, program a computer to perform a certain task. These ratings are on the same scale as a character's ratings; a challenge between a character and inanimate opposition is handled exactly like one between two characters.
Each of the two participants gets a challenge pool containing a number of points equal to her rating in the ability being tested. This pool is separate from the ability rating; decreases in the pool do not necessarily decrease the ability in question.
(It is important to realize that, although the examples presented here give complete information about both sides, in practice each challenger knows only her own ability ratings; she must guess about the other from description and its effects on her as the conflict is played out.)
The conflict is resolved over one or more rounds, which are of no predetermined length: whatever it takes to both perform the actions described and potentially resolve the entire conflict.
In each round, each challenger compares the points in her challenge pool to those in the opponent's pool. If she has fewer points, she loses as many as are in the opposing pool; if she has as many as or more than her opponent, she loses points equal to half the number in the opposing pool (rounded to the nearest whole number). These comparisons are conducted simultaneously: a loss in this round does not reduce the loss inflicted in this round.
If either challenger is reduced to 0 or fewer points in her challenge pool, she is eliminated from the challenge and loses. If both are eliminated, whichever one ends up with the fewest negative points comes out ahead (or less behind); if both are eliminated simultaneously and end up with the same number of points, the challenge ends in a draw or a double loss, as appropriate.
Akane is engaged in lifeordeath struggle with her kitchen in an attempt to prepare a gourmet meal for her fiance. Akane's cooking ability is 2, the difficulty of preparing a gourmet meal is established by the GM as being 8. On the first round, the meal, which has a challenge pool larger than Akane's, loses half of Akane's pool, or 1 (1/2 rounds up), reducing its pool to 7 points. Akane, having a smaller pool than the meal, loses the full 8 points, reducing her to 7: a humiliating defeat.
Akane, having raised her cooking skill to 3 with a few tips from her sister, attempts to prepare a cheeseburger (difficulty 3). On the first round, neither has fewer points than the other, so each loses half the opponent's pool, rounded, or 2. On the second round, they are still tied at 1, each lose 1, and both go to 0: a draw. The GM's interpretation is that Akane has only a barely edible cheeseburger, but the kitchen is a complete disaster.
Using only the basic rules, conflicts are over in one round with the obvious winner (two rounds if it's a tie). Although simple, this lacks somewhat in drama and suspense. To add those important qualities, there are three additional quantities that can be involved in a challenge.
Each point of Bonus adds to the challenger's challenge pool for purposes of determining who takes how much loss, but not when determining whether she's been reduced to zero. Bonus is commonly found in challenges that are good at actively defeating opponents, rather than passively resisting them.
Boadicca is using her ability of 6 at hunting to hunt for wild boar. She also has a boar spear, which has been ruled to give her a bonus of 2. The boar has Maul Hunter at 7. On the first round, Boadicca's total of 8 beats the boar's 7, so she only loses 4 while it loses 8, and becomes pork.
While dragging the boar home, Boadicca is jumped by a small dragon, which has Abduct Maiden 8. On the first round, being tied, they each lose half of 8, or 4. Boadicca is now at 2+2, and the dragon at 4. Next round, they are still tied, so each lose 4/2 or 2. The dragon is still at 2, but Boadicca is at 0 (the +2 doesn't help now), so although the dragon knows it's been in a fight, it nevertheless drags her off to its lair.
Points of Reserves can be sacrificed in place of points from the challenge pool, providing a buffer against losses to keep the challenge pool at its initial level. Challenges that are good at passively resisting opponents or just take a long time to deal with tend to have reserves.
Somewhat later, Dame Cecilie arrives at the dragon's cave to rescue Boadicca. She lost her sword in a bandit who discourteously fell into a deep ravine, so she has to use her dagger (getting no bonus) but still has her full armor, which gives her 6 points of reserves. The dragon has recovered any injury it might have suffered from Boadicca, so still has Abduct Maiden 8 (no, Cecilie's not married either) to her Vanquish Monster 7. Combat is joined. In the first round, Cecilie is outmatched, so loses 8 points while only inflicting 4. However, 6 points of that loss is absorbed by her reserves, so she loses only 2 from her challenge pool. Next round it's Cecilie 5 against the dragon 4, and she triumphs 3 to 1.
Resistance reduces any loss of challenge pool by an equal amount. This is very powerful, as it completely negates the efforts of any opponent with a rating equal to or less than the resistance, or less than the challenge pool and less than or equal to twice the resistance. A challenge with resistance is therefore one that opponents below a certain level can't even begin to defeat.
As Cecilie is rousing Boadicca, the late dragon's mother shows up. Being somewhat old and stiff, she only has Devour Knight at 6, but her impenetrable scaly hide gives her reserves of 4 and resistance of 4. This being a new conflict, Cecilie has her 5 points of reserves again, so makes a stand. On the first round she inflicts 7 points, of which 4 are absorbed by the dragon's resistance and the rest reduce the dragon's reserves to 1, and takes 3 points, reducing her own reserves to 2. For the second round, it's again Cecilie 7 against the dragon 6. Cecilie inflicts 7 points again, of which 3 get through the resistance, 1 is absorbed by reserves, and the remaining 2 reduce the dragon to 4; the dragon inflicts 3, which finishes off Cecilie's reserves and reduces her pool to 6. On the third round, Cecilie inflicts 6, 2 of which get through the dragon's resistance to reduce it to 2, and takes 2, which reduces her to 4. Fourth round, all of Cecilie's success is negated by the dragon's resistance, while it inflicts 1, bringing her to 3. Sensing imminent disaster, Cecilie grabs Boadicca and changes to a challenge of Run Like Bunnies.
Changing to a challenge of different abilities is easy, but whichever challenger had more points in her challenge pool when the last challenge was broken off gets a bonus equal to half the difference in challenge points for the first round of the new challenge. Challenge pools and reserves do not refresh to their full values, but do increase by the difference between the old and new ratings and reserves if the new values are higher. They do not decrease if the new values are lower, but neither can they exceed the new maxima. The bonus and resistance for the new challenge are as normal for the new abilities.
The dragon chasing Cecilie and Boadicca has Aerial Hunting 7, with 3 reserve to indicate persistence. This is one higher than the rating it used for the previous challenge, so its challenge pool is increased by 1 point, to 3. The reserve is less, however, so it does not change (remaining at 0). Cecilie's Run Like A Bunny rating is only 3, which is less than her Vanquish Monster, so her challenge pool remains at 3. Hopefully Boadicca will wake up and be able to do something useful, or it's going to go poorly for the good guys.
The same principle can be used when one challenge prepares for another, but carrying the bonus or penalty over is not optional.
Diana, crossbow moll for Caeser's mob, is trying to ambush "Fingers" Octavia before Fingers can turn Senate's evidence and bring down the Emperor of Bootlegging. Diana uses her Bushwack 5 against Fingers's Paranoid of 4 to set up for the hit. At the end of that challenge, Diana has 3 challenge points to Fingers's 1. Half that difference is 2, so Diana gets a bonus of 2 on the first round of actually trying to do Fingers in. Had Fingers had Paranoia 6, though, she would have won the initial challenge, spotted Diana sneaking up on her, and gotten the 2 bonus.
Frequently, there will be another ability, either of the challenger's or of an ally's, that is not the ability being used for the challenge but seems like it should help. This is referred to as a complementary ability, and it adds bonus based on its rating and how it compares to the primary rating: if the complementary rating is at least half the primary rating, the bonus is onequarter the complementary rating; if the complementary rating is at least twothirds the primary, the bonus is onethird of the complementary; if the complementary rating is equal to or greater than the primary, the bonus is onehalf the complementary. (For the hardcore, the bonus B = C^{2}/2P, where C and P are the complementary and primary ratings, and the maximum possible result is C/2.)
In some cases, it might be more appropriate for the complementary ability to provide reserves or even resistance. If so, the amount of reserve is 1 1/2 times the bonus as calculated above, or the amount of resistance is 1/4 the calculated bonus.
TenMeg Evangeline is trying to crack the Bank of New Orbital France with her Decking skill of 6. Fortunately, she has the logs of the last person who tried this. The GM rules this to be assistance at a rating of 3 (a bit down from the rating of the previous decker, since it's only logs). This is at least 1/2 of 6, but less than 2/3, so the bonus is 1/4 of 3, or 3/4 which rounds up to 1.
Generally, only one complementary ability applies, but sometimes there really are two. In that case, the lesser of the two modifies the greater, and then the greater one plus that bonus provides the bonus for the primary ability. No more than two complementary abilities should ever be used, or it becomes silly.
If Evangi also had the latest version of Noodynamics Data Ninja, previously established to have a rating of 2, then it would increase the rating of the logs to 4 (2 is 2/3 of 3, 1/3 of 2 is 2/3 rounds up to 1), which would put that number over the 2/3 threshhold of Evangi's 6, which gives a bonus of 4 * 1/3, which still rounds to 1. Oh well.
If, on the other hand, there is an ability that should detract from the primary ability, it provides a bonus (or reserves or resistance) to the opponent.
If Evangi instead was saddled with a copy of Microsoft Security Administrator, its annoyance rating of 3 would instead provide reserves of 2 to the BoNOF system by crashing constantly (primary 6, complementary 3, 3/4 rounds to 1, 1 * 1 1/2 rounds to 2).
Challenge points can be converted into points of the other three quantities to represent various approaches to the challenge at hand: to bonus, to represent an allornothing effort; to reserves or resistance, to indicate a cautious venture, or one that emphasizes defense. Specifically, one point from the challenge pool can be converted into two points of bonus or three points of reserves; two challenge points can be converted into one point of resistance. No more than half the challenge points in the pool at the beginning of the round can be converted. (A single remaining challenge point can be converted, with will result in an automatic loss at the end of the round, but the 2 bonus might be enough to take the opponent down as well.)
This conversion lasts until the beginning of the next round, at which time any points of bonus or resistance revert to the appropriate number of challenge points and are added back into the pool. Reserves don't automatically revert, but any or all points remaining from last round's conversion may be converted back at one challenge point per three reserve points.
After any reverse conversion is done, up to half the current challenge pool can be converted to bonus/reserves/resistance again before the round continues.
Gené is assaulted in her dreams by the psychovirus downloaded through her optic nerve by a militant Rosicrucian seperatist with a modified lasercom. The psychovirus has a strength of 5 for purposes of persuading its victim to murder the renegade Rosicrucian Himiko; Gené can use her personality trait of Loves Himiko 4 to resist the hallucinatory urgings. The psychovirus, being inhumanly patient, converts 2 challenge points to 6 reserves for the first round; Gené's player decides that since she just recently fell for Himiko, she is passionate about the relationship but it's not a deeplyrooted part of her psyche. She therefore converts the maximum allowed 2 challenge points into 4 bonus. On the first round, Gené inflicts 6 on the psychovirus, eliminating its reserves, but it inflicts 2 on her, reducing her to 0. Maybe Himiko is just using her after all...
A challenge of one against multiple opponents is conducted much the same way as multiple oneonone challenges, but with the single challenger inflicting and taking losses from all her opponents each round. Even though losses are not applied until the end of the round, this can be quite unpleasant for the outnumbered challenger.
Fu Lan (Martial Arts 10, resistance 1) is travelling peaceably through the mountains when she is set upon by the two notorious bandits Big Tang (Martial Arts 7, reserves 6) and Little Tang (Martial Arts 8, reserves 2). After some rude jokes about marital arts, they leap upon her. On the first round, each of the bandits has less Martial Arts than Fu Lan, so they each take the full 10, reducing Big Tang to 4 and taking Little Tang out entirely. However, Fu Lan takes 3 from Big Tang and 3 from Little Tang (after subtracting her resistance), reducing her to 4. On the second round she eliminates Big Tang, but is now at 2 out of her original 10 challenge pool. If Medium Tang had showed up, she would have been in deep trouble.
Alternately, a horde of faceless, identical goons can be treated as a single opponent, with abilities equal to any one of their number but with additional bonus equal to onethird the rating of one (onehalf rating for a group of more than three), and additional reserves equal to onethird the rating of one of them, times the number of members beyond the first. If it matters, each time that amount of reserves is lost, one member of the group is taken out.
Somewhat farther along the road, Fu Lan (who has fully recovered from her earlier battle) is attacked by The Seven Deaths, who are enraged not only by her shabby treatment of their idols the Tangs but also by her response of "Who?" to their declaration of their identity. Each one of the Seven Deaths has Martial Arts 5 and reserves 4; together, they have Martial Arts 5, with a bonus of 3 (half of 5 since there are more than three of them), and reserves of 8 (1/3 of 4, times six for the six extra members). On the first round, Fu Lan eliminates their entire reserve and reduces the remaining Death to 3, but is reduced to 3 herself (after resistance). On the second round, she reduces the remaining Death to 1 and is only reduced to 2 herself; on the third round, she eliminates him with no further losses on her part.
Losing a challenge means failure in whatever what trying to be accomplished, but it might also have more serious consequences. Or, it might not. Some challenges pose a threat to life and limb, while others damage no more than the loser's selfimage. It is possible for a challenge to be hazardous for one side and not for the other.
There are four points at which the penalty for losing increases: when the loser is reduced to half her initial challenge pool, when her challenge pool is reduced to 0, when it is reduced to 1, and when it is reduced to a negative value equal to half the initial starting pool.
Slightly Hazardous 
Very Hazardous 


half  1/4 ability  
0  1/4 ability  1/4 overall 
1  1/4 ability  1/2 overall 
half  1/2 ability  incapacitated 
"ability" means the ability in question is reduced by that amount; "overall" means that all the character's abilities are reduced by that amount. When calculating what the ability is for purposes of determining reductions, add half the bonus, onethird of the reserves, and twice the resistance associated with it to determine the total. Losses can come from any of the four quantities, in those proportions: one point of loss removes one point of rating, two points of bonus, or three of reserves; two points of loss removes one point of resistance.
Points from other sources can be lost, at the discretion of the owner of the primary ability involved in the challenge: allies can suffer ill effects from the loss; equipment can be used up, lost, or broken; enchantments can be dispelled, etc. No single source can be assigned more points of loss than the owner of the primary ability, however.
The circumstances under which reductions due to losing a challenge are restored are highly variable depending on the description of the consequences, but as a rule of thumb, any reduction in one ability will be restored after the next challenge involving that ability (though that challenge might bring penalties of its own), while overall reductions remain in effect until some specific action is taken to restore them, or the end of the story arc is reached.
Iridia (Sorcery 7, reserves 2) is engaging in sorcerous combat with a vile demon (Demonic Might 8): definitely a hazardous challenge! She has St Kristine's staff, which provides 2 bonus against demons, and the assistance of her apprentice Joiry (Sorcery 4, so 1 bonus for Iridia). On the first round, she inflicts a loss of 10 on the demon, reducing it to 2, but takes a loss of 8 herself, reducing her to 1. 1 is less than half of 7 but more than 0, so she loses 1/4 of her ability. Her base rating is 7, plus 2/3 for her reserves, plus 1 for her staff, plus 1/2 for Joiry's contribution, for a total of 9 (and 1/6, rounded down). 1/4 of that is 2, so she has to give up 2 points worth of ability. Since the staff is a holy relic, it seems wrong for it to be damaged, so she accepts one point herself, reducing her ability to Sorcery 6, and gives the other to Joiry, reducing her to Sorcery 3.
If the basic challenge system is too predictable, a random factor can be added by the use of dice at various points in the process. Regardless of where the randomness is added, the procedure is the same: instead of using a plain number at that point, use that number of ordinary sixsided dice. Each die counts as 1, unless it shows a one, in which case it counts for nothing, or shows a six, in which case it counts as two. The total of the dice is used in place of the number you started with for that step of the process. The result will average the same as the number you started with, but could be anything from 0 to twice the original number (though the extremes have very low probability if you are using more than a couple of dice).
Although there are several points in the process where dice could be used, it is best to choose only one of them; adding a excess of randomness only dilutes the advantage of a high rating, and slows down the action by requiring more time to be spent counting up dice.
In our second example, of Akane with her 3 Cooking and the 3 difficulty cheeseburger, things might have gone somewhat differently had dice been used. Or, they might not; that's the problem with randomness.
Using dice to form challenge pools, Akane rolls 3 4 3, for a total of 3, while the kitchen rolls 5 1 4, for a total of 2. Akane triumphs!
Using dice when comparing challenge pools, Akane rolls 2 2 2, again for a total of 3; the kitchen rolls 4 3 4, also for 3: still a tie.
Using dice when inflicting losses, each side inflicts 2 dice (half of 3). Akane rolls 5 6, for a total of 3, while the kitchen rolls 5 2, for a total of 2. Akane triumphs!
(Since neither side had bonus, reserves, or resistance in that example, the fourth option wouldn't affect anything)
Thanks to Stephen Kreamer and James Tanfor spotting omissions.
This file was last modified at 1248 on 06Jan17 by trip@idiom.com.