Monday, February 20, 2017

Active Defense

Normally, D&D is played with active attacks and passive defenses.

The attacker rolls, compares to the target's AC, and then determines if he hits or not.

Alternatively, there's the "players roll all the dice", which I like for defending because:
  • Players feel like they have more agency.
  • It frees up hands and time for the DM.
But active defense is still less fun than attacking.  When you're attacking, you're deciding who you want to attack, how you want to attack them, coordinating with your allies, etc.  Fun.  While active defense still feels very reactive.  

"The ogre tries to split you like a log.  Roll Defense minus 4."

Better than the DM rolling for the ogre and telling you that you're dead, but still just just calculations.

Ideally, you'd want to bring some decision-making into the act of defending* so that it becomes about making interesting choices instead of pulling a lever on a slot machine to see how much damage you take.

<digression>*This is actually debatable.  Do players want to have to make decisions about how to defend from five goblin spears?  Or do they just want to get to their turn quickly so they can open the cage to the dire moles and see how that pans out?  To put it another way, can we make defensive decisions interesting?</digression>

I have one other design criterion: I want the new mechanics to be completely compatible with preexisting OSR systems.

Dodging and Blocking

So here's what I got.  You have two ways to defend:  Dodging and Blocking.

Dodging works exactly the way that AC does.

Armor and Dexterity improve your Dodge; and when you dodge successfully, you take no damage.

When you block, you move into the blow and try to absorb it via your armor/shield.  You take damage from the attack, but you reduce that damage by 1 if you're wearing heavy armor, and you reduce it by another 1 if you are using a shield.

Leather Armor: +2 Dodge
Chain Armor: +4 Dodge, +1 Block 
Plate Armor: +6 Dodge, +2 Block
Shield: +1 Dodge, +1 Block

When an enemy attacks you, you can choose whether to dodge or block.

The Math

I made a spreadsheet; It's actually pretty complicated.

Blocking reduces damage equally regardless of the opponent's attack bonus.  It's just a flat reduction.  Therefor, blocking becomes useful in two situations: against enemies that 1d6 damage, and against enemies that have very high bonuses to hit, who are probably going to hit you anyway.

<digression>I think I'm going to cap the attack bonuses for the GLOG at +10 for this reason, among others.</digression>

Blocking also does another very important thing: it removes the chance that you might get critted.

Since you're reducing the spread of potential damage, you're effectively buying insurance.  You're removing the chance that you'll take maximum damage by removing the chance that you'll take no damage.

(Which makes sense fictionally, too.  Crits happen when you're trying to get fancy, jumping around all nimbly-bimbly, and you slip in the mud and take bit hit to the face.  Whereas blocking, you're just hunkering down and taking the hit on your shoulder.)

If you know you only have to survive on attack from a goblin with a 1d6 sword, and you've got 6 HP, you can play it safe by blocking instead of dodging and risking that 6 damage hit (or a crit).

You also don't want to block if you're at 1 HP.  (Makes sense fictionally: you're an inch from death, too tired to raise your shield, just trying to stagger out of the way.)

HOWEVER, if you do the math, blocking usually sucks.  By the time you have a high blocking value (platemail + shield) you usually already have a high enough AC that blocking is inferior to just defending as normal.  Still, I think the choice is interesting.  (Other people may not.)  So blocking is highly situational; dodging is the better choice nearly all the time.

Can Monsters Block?

No.  Keep it simple, keep it fast.  To do so would go against the design goals.

Metal vs Wood Shields

If you wanted to differentiate the two, you could have:
  • Metal Shield: +1 Defense, +1 Block
  • Wooden Shield: +1 Defense, can be sundered to reduce incoming damage by 1d12.

If you wanted to have a third option, you could have a Parry option, in addition to Dodge and Block.  You'd roll your attack bonus to defend instead of your armor bonus.

Except I don't want level 5 fighters running around naked, getting better defense from their daggers than they would from full plate, so maybe a condition is needed?

You can only parry when you are wielding a weapon and defending against a weapon, wielded by a human- or halfling-sized opponent.


So I just re-read all of stuff I just wrote and I hate all of it.  Normally, I'd delete the draft and go watch Star Trek, but I'm going to leave the post here because it's a good discussion.

I can explain.

Back when I played 3.5, I had a Power Attack calculator.  Based on the opponent's AC, and my average damage, how many points should I sacrifice for power attack?

I had fun doing that, because I felt clever, but now that's exactly the sort of gameplay that bores me.  It's math, instead of interesting choices.  If you know the numbers, it stops being a challenge and becomes a known solution.

So, although I just wrote them, I dislike the Dodge, Block, Parry mechanics because they're a known solution once the math is figured out.

And it's a boring problem because the two goals are directly comparable.  You're trying to choose the best way to minimize a single variable: the average damage.  Or in the Power Attack example: you're trying to maximize damage.

Fun choices come from choosing between to incomparables.  Like, should I attack with my sword (1d6 damage) or throw a molotov (2d6 damage, but is a single-use resource).  You can't boil that down to a single factor since you don't know how much you're going to need that molotov in the future.

The rule for sundering shields is potentially interesting, because you don't know if you're going to need that shield in the future.

Sundering #1: You can choose to negate all damage from an attack by breaking your shield.

Except that rule isn't that interesting.  In practice, people will keep the shield around, then break it in order to keep themselves from dying, and not a moment before.

Sundering #2: If you have a shield, you can choose to block with it instead of attempting to dodge.  Damage is reduced by 1d6, but if the base damage is 6 or more, the shield breaks.

That's more interesting.  Reminds me of the usage die, a little bit.  And it leads to some useful questions.

A bunch of goblins are attacking you.  Do you want to block the goblins with your shield?  It's numerically advantageous (in terms of minimizing average damage), but you run the risk of your shield breaking, when you might need it more later.

That's my final conclusion, then.  Block/Dodge/Parry is boring because it's a solved equation (that favors the spreadsheet-equipped munchkin) while Sundering Rule #2 is actually pretty interesting.

Need to playtest it.


  1. Nice insight into your process. I happen to love spreadsheets.

  2. I'm considering opposed d20 rolls. AC is added to the defender's roll.
    - More swingy combat. Which some people enjoy.
    - More involvement from the defender. They get to roll a dice and feel a little more in control of the situation.
    - Natural 20 on defense can mean a free counter-attack or something else cool.
    - You do this against all attackers, which can make you feel like a kung fu master. Maybe a penalty for each attack after the first. Or maybe only fighters can defend against multiple attackers. I dunno.
    - Throw in some shield blocking or parrying options for more choices.

  3. Have you ever played the war game Empires in Arms? The battle mechanic involved the attacker and defender each picking an offensive chit (attack, outflank, probe, eschelon etc.) and a defensive chit (cordon, defend, counterattack etc.) - different attacks worked better against different defences and seeing a cordon up against your eschewing could ruin your day. You could play the percentages but against a thinking opponent that's a recipient for disaster.

    Perhaps an attack choice (assault/attack/probe) vs a defence choice (dodge/parry/riposte) with different modifiers to the outcome (attack and/or damage bonus) could work, at least for duel type fights.

    1. Sounds like rock paper scissors.

      I would love to come up with a system for interesting dueling. (Maybe some sort of compromise between immediately attacking vs maneuvering for an advantageous position later?)

  4. Something I've considered in my small forays into OSR is both having an active defense roll and never having a result of "nothing happens."

    To make a melee attack, the attacks tests their Strength and the defender tests their Armor Class.
    If the attacker succeeds at his test and the defender fails at his test, the attacker rolls their weapon dice against them.
    If both the attacker and defender fail, the attacker may choose to perform a special maneuver against the defender (basically anything that required a combat maneuver in Pathfinder).
    If the attacker fails and the defender succeeds, the defender may choose to perform a special maneuver against the attacker.

    I kind of like the defender getting the upper hand during an engagement because it feels, I dunno, realistic. You're worried about moving into engagement range with a dragon because *that dragon will fight back,* and not just during its "turn."

    1. I give dragons reactions to fight back when it's not their turn.

      I'm okay with "nothing happens" because simple combat moves very quickly. On to the next player.

      Your rule *does* make it especially risky to attack things like dragons, because the dragon is going to be disarming people left and right. How would you handle tiny things with crazy high ACs, like pixies?

  5. On the subject of shields, what about "Test opposed Strength. If you succeed, you negate all damage from a physical attack but your shield breaks. If you fail, you take half damage, are knocked prone, and your shield breaks"?

    It makes it a little riskier to soak a major hit, it gives melee characters a bit more utility with Strength, and it feels like it would lead to interesting and tense moments.

    Plus, having an adorable urchin hireling (named Bismarck) carry a stack of shields for your fighter seems like an excellent plan.

    1. It is exciting, and it does help Strength contribute to survivability, and it does scale well with dragon-damage, but it's just a weaker version of the "sacrifice your shield to negate a hit" rule. Nothing wrong with that, of course, but players aren't going to use it until their HP runs down.

  6. Brendan over at Necropraxis is working on something similar. Maybe one could inform the other?

    1. I've read it, and it's good stuff, just not quite what I'm going for.

  7. What about rolling under your AC with the monster to hit bonus as a penalty? Doesn't really address the whole dodge/block/sunder issue but it would give the player a slightly more active roll.

    1. That's exactly the system that my homebrew system currently uses.

  8. Cool! Do you give players the "to hit" penalty before they roll? Or do you just tell them if they were successful or not?
    I've yet to try this mechanic in-game but I would think keeping the monster "to hit" a secret would feel more...dangerous?

  9. I totally get that you're going for gameplay options rather than strict simulationism, but do y'all know how difficult shields are to break? Its entire purpose is to get hit so you don't have to. They are very durable items. Using a bust-your-shield mechanic as described would break my immersion faster than the shield.

  10. This is another area where I really like the Apocalypse World way of doing things, players roll all of the dice in my games.
    Let's say you have a "fight" skill, in D&D that could be your 'base attack' plus bonuses, or it could be calculated as part of a matrix, or it could be just an accumulated 'to hit' number. Call it Fight!
    When a PC wants to hit something, they roll their Fight!
    When a PC wants to avoid getting hit, they roll their Fight!
    You can use either a static number to roll against or a further modifier based on an enemy's skill/size/powers/whatever.
    But what ends up happening when you simplify the roll like this, is that the player's focus more attention on what their character's are physically doing without any prompting. How many times have you had a player who, on their turn, simply says "Okay, I attack him again" without illustrating a picture of how their character attacks or what exact action they're taking to attack. With a simple Fight! roll, as a GM I narrate what the enemies are doing, how they are engaging the space, what they're fighting with, and I follow that up by saying "and this is going to give him a slight edge" or "he's at a disadvantage right now, but if you miss this roll then he's going to have you at his mercy" and this compels the players to narrate how their characters defend against such attacks, or what maneuvers they might attempt to maintain/restore the upper hand.
    Less math = more fun!