Variable

:see also Variable, Area of effect
Variable (B109) is an enhancement designed for attacks that come in levels such as Affliction or Binding or Innate Attack.
*Searching for this word in PDFs can be complicated by the term also being used for trait costs with fluctuating base values.
P107 mentions:
:strictly for attacks, which otherwise work at full power at all times.
:Non-attack abilities don’t need it – their range, area, level of effect, and so on are variable automatically.
==Examples==
sometimes things other than the 3 basic attacks are specified as using them, even though variability is assumed to be built into many advantages.
===Leech===
P142 has examples take it
===Mana Damper and Mana Enhancer===
P59 mentions taking it for them
===TBA===
==All or Nothing comparison==
This limitation has a name which could make one think of "Not Variable -5%" but AON is worth -10% for a reason: it is WORSE.
AON does not refer to an inability to control the level, but rather requires the effect of an ability to surpass a fixed threshold to have any effect whatsoever, otherwise it has no effect at all.
Examples of this modifier have been added to both attack and defense abilities:
*for attacks, if the damage does not create a certain outcome (for example: a major wound) then no damage happens at all
*for defenses, if the DR does not create a certain outcome (for example: completely reducing Basic Damage to ZERO) then no damage is subtracted at all
The difference is basically "levels are reduced to 0 if max levels don't do the job" which is different than "you may reduce levels to 0"
If one were to use AON on Partially Limited Abilities, this would mean that non-limited base/lower levels of damage/DR would always apply (always wound, always subtract) while limited higher levels would fail to apply if a threshold wasn't met. EG:
*DR10[50]+DR2(AON)[9] will stop a 12 damage attack (reduce it to 0) but a 13 damage attack would have 3 Penetrating Damage instead of 1 Penetrating Damage (because the limited DR ceases to apply)
*Crushing Attack 10[50]+CA2(AON)[9] where minimum damage is rolled on both (10+2): it requires 12 HP to cripple the limb of an HP 19 creature vs 13 HP to cripple the limb of an HP 20 creature. If the HP19 creature is hit, he loses 12 HP. If the HP20 creature is hit, he loses only 10 HP.
Other examples of AON application may exist but generally the threshold is major wound (crippling) for damage and "no penetrating damage" for DR. It would be unclear how to apply it for other stuff like Affliction or Binding.
For stuff like Fearlessness that might for example be "if you fail your fear check despite the bonus, then add AON-limited Fearlessness to your Margin of Failure, because it ceases to apply to mitigate the degree by which you failed".
*this might also for example be done to limit a Reciprocal Advantage like Not Fearfulness if one takes the Fearfulness disadvantage, for designing a Mitigator meta-trait
==Always On problems==
Although "abilities" semantically could include things classified as active ability or passive ability, when exploring the concept "user can specify their ability before USING it" (ie "before you make your attack roll" for attacks) allowing it for passive abilities leads to strange circumstances.
*if this were allowed, it should probably not be allowed for "always-on" abilities.
**for example you get an Always On discount on ALL levels of an Aura: like -40% to Innate Attack 10d [100] gives 40 points: but if Variable allowed this to be reduced to 1d then one is able to mitigate this to effectively an Always-On 1d [10] attack, where -40% only gives 4 points
***one solution to allow this concept would be to say that Variable cannot be bought for (and cannot APPLY TO) any levels of an ability limited with Always On
****so for example using Partially Limited Abilities, if one wanted to be able to dial their 4d [40] attack down to 2d (but not any lower) they would only buy Variable for half the dice, so instead of paying +5% (2 character points) on the entire ability, they're effectively paying +2.5% (1 character point) as if buying a +5% enhancement on 2d [20].
==Not Variable for Non-Attacks==
If an ability were switchable (could be turned completely off: zero levels) then there is no conceptual problem with allowing it to be Variable, but if that DOESN'T cost an enhancement (free variability included in switchable) it would make sense to allow Not Variable as a limitation on the ability if one was unable to turn off that level when the ability is switched on
*For example if you do not need to take Damage Resistance (Switchable +10% Variable +5%) to specify your DR because DR (Switchable) is Variable for free, then you could take DR (Switchable +10% Not Variable -5%) to give that.
**using Partially Limited Abilities one might specify "Fifth Not Variable -1%" (effectively taking the -5% limitation on just 1/5 or 20% of the levels) where you are forced to keep at least 20% of your DR on when using any DR whatsoever. This would save 1 character point on DR 20 [100] but leave you unable to use DR 1/2/3 because when it's switched on you must use at least 4 points of it.
==Range and Area==
It's not obvious why range/area are mentioned on P107 because B109 only mentions declaring the DAMAGE being specified before the attack roll in the example of a 3d Innate Attack
*this is the only thing the "level" of attack determines: variations in range/area are determined by MODIFIERS, not the level
**P107 might have been written with Partially Modified Abilities such as Partially Limited Abilities in mind: where modifiers are only assigned to certain levels, so those modifiers would only come into play when using those levels are specified
***due to this, the ability to specify the levels activated allows one to control factors like Range or Area even if lacking the Selectivity enhancement which allows flipping enhancements off at will: flipping the level off flips the enhancement off, with the downside being you don't have the option to use those enhancements without using the extra levels (dice/damage) which gives less freedom (can't do non-lethal low-damage attacks at long ranges or large areas, for example)
P173 mentions the possibility of adding it as a Temporary Enhancement under P172's "Improving Attacks"
==Damage Resistance==
DR is a non-attack ability ("Ability" presumably meaning ADVANTAGE: there's no implication in P107 that non-attack TRAITS don't need variable: you can't will yourself to use fewer than maximum levels of Fearfulness or Magic Susceptability for example) but there does not appear to be an option to "will oneself to have less DR". That would basically give Switchability for free when it is a +10% enhancement.
*That's normally a no-no except in Chinese Elemental Powers where it's argued that 0% is appropriate for base DR since there are no drawbacks 
**(which is incorrect since it's a drawback to resist desired afflictions/drugs/blood-tests or appear to be inhuman when you want to pass as mundane)
The "variability" of DR could be perceived as "as much DR activates as is necessary to apply to the attack". So for example if hit for 0 damage, no DR "activates", 1 level activates against 1, 2 levels activate against 2, etc.
*this could apply to No Wounding attacks too: B109 allows DR to protect against Side Effects which operates purely on there is Penetrating Damage, even if it is Penetrating Non-Wounding Damage.
**this would also mean it could "variably activate" against a No Wounding attack that lacks No Blunt Trauma, even though Basic Damage being stopped by Flexible DR is the condition which allows Blunt Trauma to injure someone
***this actually means it is better for Non-Wounding Crushing Damage 5+ (10+ for other physical) to penetrate flexible DR so long as it does nothing else (like Side Effect) since failure to penetrate means suffering HP loss to BT
****due to this, if one knows one is being targeted by NWCD it is better to reduce one's flexible DR to 4 or less (9 or less for non-crush physical)
The complication arises here because while variability on ACTIVE abilities is easily understood (B41 Breath-Holding or Chameleon or Charisma for example: you're not forced to hold your breath or to blend in or be charming, B52 you're not FORCED to use full levels of Enhanced Move, B53 you're not FORCED to use Enhanced Tracking) assuming "variable level control" on PASSIVE abilities (B21 Appearance Levels, B41 "Always-On" Chameleon, B53 Extended Lifespan) is a strange thing.
Some leveled advantages (like Fearlessness or B58 Hard to Kill) while passive, don't really have much incentive to be made Selective/Variable unless one WANTS to be intimidated or fail fear checks (the ability to will oneself into stun/madness)
==Levels influencing modifiers==
There is a concept called Declining Enhancements which PU4p17 describes as differing from enhancements remaining equally potent as higher levels of an ability are unlocked. Zzap whose Accuracy is lost when doing higher-damage Burning Attack is used as an example.
*This is basically a variation on Ascending Limitations which can be viewed as using Partially Enhanced Abilities or Partially Limited Abilities in many (but not all) cases: losing Accurate +5% by going up a level is the same as gaining Inaccurate -5% by going up a level.
Both concepts assume "one will tend to want to use the higher levels" and not doing so creates exploits which should alter the pricing structure, if it allows for point savings at all:
*limitations increase as levels rise
**with reverse Declining Limitations one could just use the ability at full power to ignore the limitations
*enhancements decrease as levels rise
**with reverse Ascending Enhancements one could just use the ability at full power to make full use of the enhancements
The effect in both ESTABLISHED cases (modifier value is lost as higher levels are used) is that pricing is done for the approximate average/midpoint of possible levels. This:
*gives a large discount that has minimal drawbacks when using the ability at low levels
**eg Zzap gets Acc+6 (Acc9) for +17% (16.25 rounded up) instead of +30% 
***however this is on Burning Attack 12d which has a base cost of 60 points. +17% costs 11 (10.2 rounded up) character points, increasing the cost of the ability to 71 character points
****double-rounding like this might be seen as unfair: GMs enforcing non-decimal CP costs might still allow decimal enhancements (16.25) to be used to calculate CP cost of an ability and only rounding up once at the end: 116.25% of 60 for example is 69.75 character points which rounds up to only 70, not 71 as when rounding up at both steps.
Note however that +30% for this Acc where it actually applies in full (the first two levels) applies to a base 10 points (Burning Attack 2d) which would only cost THREE character points.
*For Burning Attack 2 [10] he'd pay +30% for Acc+6 (9) and 3/10 of 10 is 3cp
*For Burning Attack 4 [20] he'd pay +25% for Acc +5 (8) and 1/4 of 20 is 5cp
*For Burning Attack 6 [30] he'd pay +20% for Acc +4 (7) and 1/5 of 30 is 6cp
*For Burning Attack 8 [40] he'd pay +15% for Acc +3 (6) 15% of 40 is 6cp
*For Burning Attack 10 [50] he'd pay +10% for Acc +2 (5) and 1/10 of 50 is 5cp
*For Burning Attack 12 [60] he'd pay +5% for Acc +1 (4) and 1/20 of 60 is 3cp
The total for all that is 28 character points, more than the 10 or 11 extra points which Zzap would need to pay.
This might be compared to viewing them as Alternative Enhancements.
The most expensive is 6, so dividing the remaining total (22 points) by 5 gives 4.4 character points for a total of 10.4
==Where DR variability would matter==
Disadvantages can come in levels, so Temporary Disadvantages via Partially Limited Abilities could be used to construct Ascending Limitations too.
This is easier to understand when defining distinct abilities:
*DR (Switchable, Crushing Only, Temporary Disadvantage: Fearfulness 1)
*DR (Switchable, Cutting Only, Temporary Disadvantage: Fearfulness 1)
If a character with both of these switched both on, he would suffer the effects of Fearfulness 2. If he only had ONE on, it would just be Fearfulness 1.
*Link +10% would allow these to be switched on with a single ready maneuver, but force you to activate them together, so Fearfulness 1 would not be possible.
==Variable for free==
Page 9 of GURPS Power-Ups 4 says this is built into melee attacks (unarmed attacks) when designing ST-Based damage as a Crushing Attack, probably indicating how you can opt to use any ST from 0 to your max.
*This was mentioned somewhere in the basic set as pull punch or similar
==Turning off built-in variation with a new limitation==
To design someone who can't do that perfectly (like how you need to roll 'pull punch' in Palladium games to do less than max damage) you would need to design a Not Variable limitation to remove it (a Reciprocal Limitation) to enable buying Variable to get it back.
*This could then be limited with something like Requires (Attribute) Roll, for example the ability would only be Variable if a DX roll was passed.
**To get a more variable effect (less "all or nothing" then hitting at full power or hitting at any amount less) would require using the "margin-based" rules.
In this case, somehow the amount you succeed in the skill check determines how many levels of your attack are variable. If the MoS is enough to cover all levels, it can be reduced to nothing. If it's only enough to cover a few, only those levels can be removed and the leftover must do damage.
*Margin-Based is designed for resistible abilities, either a 1-sided roll by a target or a quick contest against them by the user
**so it might normally be unfair to allow it
***in this case though since the idea is to BENEFIT the target (to allow the attacker to do less than maximum dice to them) one might actually define this as Resistable but then assume targets inherently WAIVE resistance (unless they WANT to take maximum damage)
==turning off built-in variable with an alternative==
Alternative Enhancements is another way: buy a new enhancement alternative to the built-in Variable, while using that alternative you cannot use variable. That's another way to turn it off.
==Counter Enhancement==
*Not Variable
==See also==
*Ascending Limitations
*Cancellation
*Costs Fatigue, Variable
*Limited by Margin
*Margin Based
*Pull your punches
*Selectivity
*Switchable
Category:Enhancements