Monday, April 26, 2021

Shooting at Groups

For your consideration: Here's a new rule I recently drafted for my OED House Rules to handle shooting into large groups of combatants (like into a melee, or an advancing goblin horde). I'm actually kind of delighted by it, but I fear I might be the only person willing to actually implement it.

First, recall a few things about how I run my OD&D. I use a ranged modifier of −1 per 10 feet distance, because that matches a rather large amount of research we've compiled on the blog in the past. Second, I'm working on the continuing project to dial in mass-warfare mechanics well for the Book of War game (hopefully in an upcoming 2nd edition). 

Both of these goals span the man-to-man case and huge-army cases. An aphorism I now use as foundational is: Shooting a man at a hundred yards is impossible, while shooting an army is certain success. (Practically speaking.) Previously in OED I had two different rules to handle the two different cases. The binary switchover has troubled me for a while, and raised a few reasonable questions recently. (I dare say in my head this echoed the conflict in physics between relativity and quantum mechanics.)

So I did some computer simulations and scribbled out some math (I'll spare you that here), and then realized that I could round things off to a rule I could hold easily in my head, and give a smoothly continuous switchover between the two cases. So here's what I just edited into my next draft of the OED rules. First:

Errant Shots

Errant Shots: Fumbled or random attacks into groups are assessed with a d20 roll that ignores attacker skill and range modifiers.

Like the text says, this is a mechanic that I will (and have in the past) used for a few different cases. If someone gets in a fumble situation where they attack themselves or a friend, we invoke this. (Rules where a fumble results in automatic-damage against a heavily armored ally have always ground my gears, or even a normal attack roll as if the fumbler was aiming the perfect attack against a weak spot.) Also a shot against a faraway, large group will trigger this mechanic. (Likewise: close-up an archer should be able to target a vulnerable point on the target, whereas far away this level of skill is impossible.) 

To be clear, in an "errant shot", the attacker's base attack bonus gets ignored. I would want to apply the defender's AC as usual, and I guess also any weapon-vs-armor effect, and magic as well. But to date any time this has happened for me it's just the player rolling a raw d20, and me applying the defender's AC (under the standard Target 20 resolution process). Now consider this:

Shots at Groups

Shots at Groups: Attack rolls (including range, but before AC addition) below 10 miss a man-sized target. Each adjacent man gives a 1 pip chance under 10 to trigger an errant shot against a random target in the group.

As usual, I write that with some curtness in the document. What that means is for a close group of N man-sized combatants, the DM computes 10 − N, and an attack roll from that number up to 10 indicates a shot that completely missed the individual target -- but, close enough to possibly strike someone else nearby (randomly determined, and adjudicated the with the "errant shot" rule above). Some examples:

  • Say an archer shoots at an opponent in melee with a single one of their friends. Then a modified attack roll (again: including range but before target AC is considered) of exactly 9 -- no more and no less -- triggers an errant shot against the friend.
  • Next, the archer shoots at a squad of 5 men-at-arms approaching angrily. In this case an attack roll of 5-9 results in an errant shot check against a random one of the men.
  • Ten goblins are running together down a hallway and the shooter makes an attack. Now an attack roll of 0-9 results in an errant shot.
  • A formation of 20 orcs is posted outside a cave. In this case, any modified attack roll from −10 up to 9 triggers an errant shot. 

As you can see, for very large groups at very long range, the mechanic makes it more and more likely that an errant shot against a random target will be invoked. Obviously, the DM should be encouraged to round these numbers off to convenient values -- myself, I'd probably round it to units of 1, 2, 5, 10, 20, etc. I've set it up so the lower bound is found by subtracting from 10 to make it as easy as possible. 

Moreover, the DM should be encouraged to invoke the errant shot rule immediately if it's clear that the shooter simply can't hit an individual man-sized target at the range in question. As a quick rule-of-thumb, if the range penalty is 10 points more than the shooter's fighter level, then they pretty much can't hit anything without a natural 20 (and you should just break to the random shot immediately).

To be completely clear, we're assuming that attack rolls that score 10 or higher are actually on-target, but are fended off by the person's armor if the final resolution (including AC) fails to indicate a hit. Note that this mechanic simulates attack values just a bit below hitting as indicating arrows zipping close by the target (the lower the roll, the further away). And it also allows you to separate out the effect of a critical-miss (natural 1), if you so choose. 

Let's momentarily consider a possibly alternative rule that comes to mind: If a shot doesn't hit, then a natural die-roll in the range from 1-N against N men triggers an errant shot (ignoring natural-1 fumbles momentarily). Seems nice. But the problem here is that it loses visibility of the range in which the shot was actually on-target but stopped by armor (which should be significant for heavily-armored figures). I suppose you could say that a roll of 1 - N (for N men) triggers an errant shot, unless the modified roll is in the range of 10 + AC to 20, in which case it was stopped by the original target's armor. But now you're tracking two different ranges instead of one, and that seems worse to me. (Plus this implies that both very high and very low rolls indicate close-to-the-target shots, while rolls in the middle indicate shots further away, which feels confusing and wrong.) So I would shy away from that alternate proposal.

Aside from all that, another thing that fairly excited me was that the same piece of math that generated this rule also spawned a really nifty rule for handling missile shots in Book of War at targets of unusual size, like solo heroes on the field -- but more on that later.

What do you think of that rule? I've used what I'm calling the "errant shot" mechanic before, but haven't tested the "shots at groups" at the table before -- but I'm pretty confident that would work for me. Would you want to try using that? Anything I could improve in the explanation?

30 comments:

  1. Just to get it straight, you're proposing roll to hit with bonuses and range penalties vs AC, if that misses roll to see if there's an errant shot based on number of adjacent targets, then roll to hit with no bonuses or penalties vs AC,and if that misses you're done? Just trying to get it clear.

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    1. Correct; two rolls maximum. The first roll is checked for errant-shot-iness before the AC gets added in.

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    2. Ok, I think I see. I'm going to have to grab an envelope and scribble a little.

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  2. Just to make sure I understand - the procedure with this rule is:
    1: Check if (modified) attack roll is >=10, if so resolve the attack normally against the intended target and their AC
    2: If attack roll is not >=10, check if attack is close enough to hit someone nearby, with a roll between 9 and 10-N (where N is the number of nearby people other than the intended target) indicating this is so
    3: If a nearby target is indicated, determine randomly who it is
    4: Make an unmodified (by natural attack bonus or range, but still modified by magic) attack roll against that target and resolve it normally vs AC


    Seems reasonable, though I really want to merge steps 2 and 3 somehow. Perhaps by assigning each nearby target one of the "errant shot" numbers, so there's no need for a second roll to determine the errant target. Obviously doesn't work if there's more than 9 nearby targets (unless you allow negatives), but tbh I'd be fine just capping it at the 9 closest errant targets. Or 8 closest if we're on a grid, keep it simple.

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    1. I see what you're saying (include the random determination of errant target in the initial roll). That's actually really clever. I should include that!

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    2. Thanks! Yeah, always nice to squish rolls together where possible.

      I did have one other question - what happens if you're shooting at someone with a worse AC than unarmored (e.g. DEX penalty)? Does the start of the errant range just move down? I don't recall offhand if that's even possible in 0e though, maybe not.

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    3. Another good point, I guess I hadn't considered. I guess yes?

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  3. I really like this and will try it out. It seems like a good model for shooting fish in a barrel (which I’ve never really seen before) as well as a the dangers of firing into melee. My current rule is that the total must be 20+ else it hits a random target and that feels a bit punitive while also ignoring some actual hit rolls. Now I need to develop a super simple code for this that fits with my minimalist hr booklet. This is what I have so far for my AAC game: Errant Shot: Raw d20 throw vs AC
    Shots at Groups: Total attack throw < 10 misses target but each extra fighter = 1 chance to trigger an errant shot Vs close combatant. Ex. Errant shot vs two man duel triggered on throw of 9.

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    1. That's a nice way of putting it. Thanks for thinking about that!

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  4. I'm a little confused. OED unarmored AC is 9, right, so an unmodified 10 isn't on-target, why are these rules written as if it is?

    Also one part says "the DM computes 10 − N, and an attack roll from that number up to 10" which seems inconsistent with the rest of the rules that clearly say it goes from [(10-N)..9].

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    1. Unarmored AC is 9 but that's with descending AC and characters starting with a THAC0 of 19 IIRC - so you hit unarmored on a 10.

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    2. I shouldn't have said "unmodified". This is looking at the attack roll result after range and attack bonuses but before the AC is taken in.

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    3. I agree that a roll of 10 isn't a "hit" against AC 9; I might say that it's a grazing shot that doesn't do injury? (i.e., still essentially on target, not at another person) Partly just for simplicity of the "look for a single digit" mechanic.

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    4. Oh the hole at 10 is deliberate! Interesting. Yeah I was thinking it could be one of those arrow-in-the-hat, bullet-bounces-off-the-canteen kind of deals.

      51% joking: Almost implies that the true naked AC is 10, but clothing and equipment gets you up to AC 9!

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  5. There seems to be an inconsistency in your calculations.

    In the example with 1 goblin fighting 1 ally, your math agrees with the original statement that "Each adjacent man gives a 1 pip chance under 10 to trigger an errant shot against a random target in the group" - since there is one person adjacent to the goblin, there is a 5% chance (attack roll of 9) of hitting that ally. However, this does not agree with the statement that "for a close group of N man-sized combatants, the DM computes 10 − N" - this computation with a group size of 2 would indicate that an errant shot occurs on either an 8 or a 9 on the attack roll.

    The latter examples, however, do hold to the "10 - N" computation, while being off-by-one compared to the "1 pip per adjacent target" wording. For example, in the group of 5 men-at-arms, there are only 4 other soldiers adjacent to the original target of the arrow, yet the given range of 5-9 is 5 pips which result in an errant shot.

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    1. Indeed, this tripped me up a little bit as well while trying to parse the examples.

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    2. Rats, that's a good point. I guess I need to iron that out. Thanks for the bug report.

      I guess we have two options there: (a) subtract from 10 one less than the number of people in the group (i.e., don't count initial target), or (b) subtract the whole group number, but let in the possibility that the errant shot is back at the original target.

      What do you think would be better/easier?

      (or I guess use the alternative method of 1-N, with 1 being a fumble instead of counting the original target)

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    3. I could go either way on that one but think I would find it easiest to work with 10 minus the size of the group. The fact that the original target might still be hit is an interesting wrinkle that players would certainly not mind.

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    4. I'm pretty sure that if I ran this, I'd go with the 1-N, 1 is still an automatic miss. It's just less math, and I don't have strong intuitions about adjacency being meaningful.

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    5. My instinct would be to not include the original target in the list of possible errant shot recipients - but reserve the right to require the initial attack roll (rather than immediately skipping to random targets) if players get any bright ideas about shooting at the princess from far away and killing her kidnappers with errant shots while leaving her unscathed. So yeah, I would go with any shot in the range [11-N,9] being an errant shot.

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    6. Joshua: I also kind of wish I could use 1-N, it would be so simple.

      But it creates a problem with very long range possibly making a low or null-chance of getting close to the whole group. Example: Shooting at 10 men at 300 feet (assume +0 attack bonus, and ignore any nat1 or nat20 effects). Then the errant range would be 0-10, but the modified attack roll (with -30 to hit) would be -30 to -10, indicating that a shot on-group is effectively impossible (which is the point of the model). If I blindly assumed 1-10 is still errant on the group, that would be in error.

      I might be off by 1-point here or there in the example for simplicity. Or maybe I'm overlooking some other correction. (Late as I write this.)

      I think if we had to compute the number of pips for the errant chance directly it would be min(men, men + mods + 10), ick.

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    7. Maybe I'm slow this morning, but I'm not seeing the problem, as long as you apply the already calculated range penalty to the errant shot. Is there a crucial difference between calculation of errant-ness including range penalty then roll to hit without penalty, and calculation of errant-ness without penalty and roll to hit with penalty? In the cases where the range penalty is large enough to make the actual roll moot, is there even a difference other than it's probably easier to see no conceivable roll will hit a target than no conceivable roll with fall within the calculated errant range?

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    8. Yeah, I think so. It comes back to the essential "can't hit a [particular] man, can't miss an army" at very long range.

      With that example I had just above (-30 to hit from range), it automatically flips to the errant-shot case. But that errant shot shouldn't automatically miss, because it lands _somewhere_ inside a big army formation, and should have a legit chance to stick into a guy somewhere (depending on armor only, I'd argue). Applying the -30 to the errant shot roll so it's impossible to hit anyone is not the same thing.

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  6. The rule as written for OED is crap. Your attempt to be concise is useless if it isn't understandable. Are you going to include an endnote directing readers to this post? Would you enjoy a set of rules like that? Here are the rules and here are the links that explain them. Either include an explanation in the rules or write the rule more clearly.

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    1. OED is a set of Dan's personal house rules that he was kind enough to share with us. They are always evolving and include numerous notes and links to other products.

      They aren't perfectly polished nor try to be (one day maybe). And yet Dan make them available and written in a really organized fashion to be used with ease.

      Manage your expectations.

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    2. Actually yes, all of my OED house rules documents at OEDGames.com are written that way, and so are all my future releases. The reader gets a very curt statements of rules as a brief in-play reference, and then extensive endnotes that usually outpage the rules with expansions, historical citations, comparisons of different editions, legacy comments by Gygax or Arneson or their players, further explanations, options and variants, etc.

      It is actually my preferred format for rules now in this indie/DIY space. YMMV of course. Thanks for asking about that, actually.

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    3. I hadn’t really thought of that but I like it. I have been maintaining a very tightly arranged zine booklet of my home rules the last few years but have started to build up a second shadow document of elaborations and explanations that I don’t want to get in the way of quick reference. An appendix of footnotes seems obvious now I say it but that may be what I do for my next update.

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    4. Daren, thanks for your thoughts on that! Good feedback.

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  7. This has the potential to dovetail nicely into massed combat. So you shoot into a mass of troops and the accuracy is determined more about how tightly packed the targets are (Target number is 10-N, where is N is the number of targets within a certain distance, 10'?5'?. 1 target would be hit only on a 5%.). Is your target in close ranks, very close ranks, skirmish etc... Sometimes it is better to just shoot at the crowd. Trade-off would be you dont get to pick your target as it is just some random target in the crowd.

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