Thursday, June 7, 2012

Level-scaled combat and analysis

My last two posts focused on the combat system in D&D as written, and how the faults of the system, insignificant at low levels, will eventually cause combat to break down into boring slogs or equally boring routs.  Now, I want to take a closer and harder look at an alternative system I tossed out almost as a throwaway, but which is quickly growing on me.

I proposed recently that attack rolls could be determined by comparing the levels of the combatants, and applying the difference between them.  For example, a 6th level fighter against a 2nd level fighter would attack using the THAC0 or attack matrix of a 4th level fighter.  The lower level combatant attacks as 1st level, regardless of how many levels inferior he actually is to his opponent.  I suggested some adjustments for other classes, to reflect their lesser combat ability relative to fighters.

After a little more thought, it seems to me that it would function a lot more smoothly, and with fewer fiddly calculations at the margin, if it was based on an Attack Bonus framework rather than THAC0 or a class-and-level based attack table.  (A little more granularity would also be nice; i.e. spread out those +2 jumps into more frequent +1s.)  The Dark Dungeons retro-clone has calculated Attack Bonuses for each class and for monsters in a way that lines up pretty well with the attack tables from Classic D&D, with the aforementioned granularity, so I'll use those numbers.

Each Armor Class has a target number for a hit - for example, to hit AC9 a 10 must be rolled, and this remains constant regardless of class or level.  These numbers will be equivalent to the line of the attack table for 1st level characters, i.e. a THAC0 of 19.

When creatures or characters attack each other, compare their Attack Bonuses, and subtract the lesser one from the greater.  The one with the greater initial AB gets this difference as a positive modifier to his attack roll.  The lesser rolls unmodified.  In effect, the Attack Bonus of the lesser goes toward neutralizing much of the advantage of the greater.  If two AC9 characters are fighting, and one of them has an Attack Bonus one point higher than the other, one will need a 9 to hit, and the other a 10.

The upshot of all this is that a character fighting an evenly matched opponent is going to need about the same number to hit, whether he's 1st, 11th, or 21st level.  If he's fighting a much less skilled opponent, he's still going to be superior.  The greater the difference, the easier it is for him to hit.

Under this system, characters don't need to constantly upgrade their armor to try to keep pace with escalating attack rolls.  The thief's leather armor never becomes obsolete.  He's still lightly protected, as he was at the beginning.  Wearing light armor to maintain a rapid movement rate is no longer such a lopsided tradeoff.  A lightly armored swashbuckler is no more disadvantaged by her choice at 25th level than she was at 1st.  She doesn't need absurd magic items like bracers of defense AC 0 to make her style viable.  The game master doesn't have to slip into Monty Hall mode when handing out magic armor and protective gear.

With the AC arms race blunted, outrageous negative ACs will be far less common, allowing low level opponents to be more of a threat to high level PCs.

As I mentioned in the first post in this mini-series, high level combats are going to take longer when combatants aren't hitting and doing damage each round practically at will.  Using this system, it makes a lot of sense to compensate by increasing the damage potential of high level characters.  Weapon mastery, as detailed in the Master Set or the Rules Cyclopedia, fits into this system far better than it does in the original, in my opinion.  Escalating damage and increased frequency of hits together seem like massive overkill.  Alternatively, simply bumping up the damage potential of all weapons a class can use at certain levels will work just fine too.  The first upgrade might be to one die larger than the base damage, then to two dice one size lower than base damage, then to two base damage dice, then two dice one size larger than base.  1d4 becomes 1d6 becomes 2d3 becomes 2d4 becomes 2d6.   1d6 becomes 1d8 becomes 2d4 becomes 2d6 becomes 2d8, and so on.  Fighters and dwarves get upgrades at levels 6, 12, 18, and 24.  Clerics, thieves, elves, and halflings upgrade at 8, 16 and 24.  Magic-users upgrade at 12 and 24.

This system is also a natural fit with multiple attacks.  As written, there's no cost to multiple attacks, and no reason to choose a single attack if you have the option for multiples.  Consider the possibility that attacking multiple times means that you have to divide your Attack Bonus by the number of attacks, though.  Now, the choice to take extra swings will mean that you either sacrifice part of your advantage, or give a greater advantage to your opponent.  A fighter with an AB of 8 attacking a dragon with an AB of 10 once per round gives the dragon a +2 bonus to hit him.  If he attacks twice per round, the dragon's advantage becomes +6.  He certainly can rush the beast in a whirlwind of steel, but at the cost of being less able to defend himself.  If the fighter's Attack Bonus is 16 to the dragon's 10, his bonus to each attack would be +3 instead of +6.  In that case, he sacrifices accuracy to attack in a flurry.

It could also be used to make surprise attacks and missile attacks, which are hard to defend against, more deadly relative to ordinary melee attacks.  The attacker in those cases might get to use his full Attack Bonus unopposed, or opposed by only half the target's AB.  You'd definitely want to use rules to make firing into melee hazardous, or missile weapons would have an unqualified advantage over melee attacks.

Is this still D&D, or has it become something else?  Is it old school compatible?  I don't know, but I'd like to give it a try.

23 comments :

  1. It essentially converts the part of your attack bonus that matches your opponent's to an AC bonus. Basically, this favors low level characters since they don't have much bonus to take away. I'm intrigued.

    One issue though would be revealing enemy capabilities to players. I know some people don't mind telling players AC or even HP of enemies, but I like to conceal those numbers. Thus, the ref would need to do all the math. Might still be okay though.

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    1. I had some misgivings about that too. I think the solution of the DM doing the math should be workable, though, since there really doesn't seem to be a whole lot of numbers to crunch. I really wish I could get the group together and try it out soon. Results will be posted whenever that happens.

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  2. i like it. thinking about it now...

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  3. Esssentially: everybody adds their attack bonus to their own AC.

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    1. Except that it takes away from your opponent's attack roll rather than augmenting your AC, so if you are a 10th level fighter, 2nd level and 8th level fighters have the same chance of hitting you (because you stole all their attack bonus with your skill), but you have a much better chance of attack against the 2nd level fighter than against the 8th level fighter.

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  4. Ok, so wait, the weaker party subtracts the bonus difference from his/her own AC?

    I like it, but I can't think of any way it doesn't require calculating that every single time--which is an extra step in combat. Good for duels though

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    1. The stronger party gets the difference between its attack bonus and that of the weaker added to its attack roll. AC as such isn't modified. If two fighters in chain mail are fighting, and one has a +6 AB and the other has +4, they're both still rolling to hit AC5, and need a total of 14 to hit. The first one gets to add +2 to his roll, and the second gets a straight roll. Only one extra calculation per combat; subtracting the lesser AB from the greater.

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    2. This comment has been removed by the author.

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    3. Yes, but effectively adding the difference to the attackers bonus is the same as lowering the defender's AC by the difference. It's the same math, yes?

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    4. Ah, yes, I get what you're saying now. For some reason, adding the difference to the attack bonus seems like a simple operation in my mind, while applying it to AC makes my head swim a bit.

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    5. Attack ROLL! Adding the difference to the attack ROLL is a simple operation. Now that everybody's probably thoroughly confused, myself included.

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    6. Subtraction keeps the numbers small though, which is nice, and is psychologically good for combating bonus inflation, I think. Just because the math is the same doesn't mean that it works the same in our heads.

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  5. Interesting stuff. I considered a similar idea where characters do away with AC and instead rely on a class-related 'Combat Bonus' roll-offs with d20s. I don't know if it's still 'D&D', but whatever you're doing, you aren't the only one thinking and experimenting in these directions. Please keep us informed!

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  6. Are you on Google Plus? We have a thread going on there about this too.

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    1. I do have an account there, but haven't made much effort to figure out all the bells and whistles yet. How do I see the thread?

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  7. I want my DM's to see this. I want to try this.

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  8. I just want to double check my math.

    It is possible to run this behind the screen without ever requiring the players to do calculations.

    A gnoll with an AC 12 and an attack bonus of +3 can be considered to have an armor class of 15 (12+3) versus all attacks.
    When attacking a first level wizard (AB+0) the gnoll attacks at +3.
    When attacking a first level fighter (AB+1) the gnoll attacks at +2.
    When attacking a fifth level fighter (AB+5) the gnoll attacks at +0.

    Correct?

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    1. No, the gnoll does not get the full AC bonus against, for example, an attacker with +1. Think about the gnoll attack bonus subtracting from the attacker's attack bonus rather than adding to the gnoll AC. (Sorry for that tangled English.)

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    2. Right, but they are mathematically equivalent?

      Subtracting from the attack bonus is the exact same thing as increasing the AC? Or am I wrong?

      The reason I suggest doing it this way is because it requires that the player do nothing, and allows me to pre-calculate everything, except for what the gnoll needs to hit.

      Right? or is something wrong with the math?

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    3. +0 BAB, AC 10 vs. +3 BAB, AC 10:
      number required to hit: 10
      (Effective bonus of 0 to AC.)

      +1 BAB, AC 10 vs. +3 BAB, AC 10:
      number required to hit: 10
      (Effective bonus of 1 to AC.)

      +3 BAB, AC 10 vs. +1 BAB, AC 10:
      number required to hit: 8

      Note the first two cases, the defender is identical but the math is different because the attacker has a different BAB between the two cases.

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    4. (In above examples, A vs. B, A is attacking B, B is defending. In case that wasn't clear.)

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    5. Right. So you can't just raise the AC, because If you do, then the +0 fighter needs a 13 to hit and not a 10.

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