# Target 20 as new to-hit mechanic?

#### Walker N. Waistz

##### First Post
After this thread linked to Mike Mearls's old blog, I poked around some more and looked at when he was running AD&D (not his more recent 1981 D&D rules game). He noted he was using some house rules, including "Delta's Target 20", which I checked out.

Basically, it is "Roll d20 + attack bonus + AC". You always hit on a 20 or higher, or miss on a 19 or lower. (This is based on the era when lower AC was better). Attack bonus was defined as level for a fighter, 2/3 level for a cleric, 1/2 level for a wizard. Blog entry is here: Delta's D&D Hotspot: What is the Best Combat Algorithm? Mearls even comments on the blog entry and indicates WotC might be receptive to this mechanic.

Anyways, I was just wondering if anyone thought this is the way it might go. I do sort of miss descending ACs, though I am not sure why. But always having the same Difficulty for an attack roll is sort of nicely intuitive.

Someone may have posted this before, in which case I apologize for the redundant post.

#### BobTheNob

##### First Post
Cant say I miss descending AC. Any like of it is purely nostalgic.

That said, I kinda like it more like this
d20 + attack - defence. an 11 or greater is a hit

This allows that
* higher defence is better
* Attack and defence can be on the same scale

Actually very close to the original model in probability, but allows that attack and defence numbers are scaled the same and can be easily compared

#### Herremann the Wise

##### First Post
I'm not a fan of the 20 as a target idea. I prefer the target to be variable and representative of difficulty thus immediately informing me in a minimum amount of space as to the difficulty of a particular task.

Further, I like the idea of an absolute (rather than relative) set of target DCs ala that old 3.x table. DC 0 can always be performed by someone who is unimpeded, while a DC 40 is at the limit of mortal endeavour.
I still remember that DC 43 survival check:
* Track a goblin that passed over hard rocks a week ago, and it snowed yesterday.
** Who could do it: A 20th level ranger who has maxed out his survival skill and has been fighting goblinoids as his favored enemy since 1st level.

Best Regards
Herremann the Wise

#### triqui

##### First Post
I'm not a fan of the 20 as a target idea. I prefer the target to be variable and representative of difficulty thus immediately informing me in a minimum amount of space as to the difficulty of a particular task.

Talking about attack, theres no real diference. And talking about skills, there's not either, if DC are modified to a bonus/malus to the roll.

DC 15 in a normal roll is exactly the same as DC +5 with target 20. DC 25 is the same as DC -5 with target 20.

#### Herremann the Wise

##### First Post
Talking about attack, theres no real diference. And talking about skills, there's not either, if DC are modified to a bonus/malus to the roll.

DC 15 in a normal roll is exactly the same as DC +5 with target 20. DC 25 is the same as DC -5 with target 20.
I understand that mathematically, there is no real difference, but I find it easier to have that modifier baked into the DC rather than forced out to maintain the 20+ equals success thing.

I think the core mechanic of 3e/4e is the best evolution of this and represents the core D&D mechanic distilled into its purest form. Personally, I would like to see the mechanic furthered (and further complicated) by having a double DC; to provide three possible outcomes rather than two. This would allow some truly funky designs to be thrown into the mix, to better model the outcome of a task. But that's just the inner mathematical nerd in me wishing a little too hard I think. Still, with a double DC, you can do some truly awesome things.

Best Regards
Herremann the Wise

#### trancejeremy

Cant say I miss descending AC. Any like of it is purely nostalgic.

I dunno, while it was later abandoned, one of the nicer things was that it basically constrained AC from 10 to -10.

3e suffered (IMHO) from an inflation (explosion, really) in combat numbers - hit points, AC, etc, for both characters and monsters. Was it really needed? Why not stick to a smaller scale, rather than exploding everything to ridiculous numbers...

#### Libramarian

When I was running Basic D&D I used THAC0, because I didn't want to use a DM screen or any tables, I wanted all the rules in my head.

I considered "target 20" but I came up with this which I like better:

Roll d20,
- if 11-20, attacker compares to THAC0, equal or greater = hit.
- if 1-10, defender compares to AC, equal or greater = miss.

Both THAC0 and AC are like saving throws: roll over, something good happens. No mathematical operations required, just 2 comparisons.

Now that I'm running AD&D I use attack tables, because I need a DM screen for rules reference, so I might as well put more tables on there.

#### Serendipity

##### Explorer
Interesting. Not that I have any desire to go back to the "AC runs backwards" era, but it's not something that would stop me from opting into a game as a player.

#### dkyle

##### First Post
Target number 20 seems completely silly to me. I don't see any redeeming value to it at all compared to d20 + bonus, compared to a DC. It's basically replacing a comparison to a variable number, with an addition of a variable number, plus a comparison to a static number. Comparisons are faster than additions, generally, especially since "target 20" requires communicating the DC to the player, whereas "target DC" does not. It's just seems different for the sake of being different.

Descending AC is silly too, but at least there's nostalgia value to it. But any and all mechanic properties of descending AC can be represented using ascending AC, with the benefit of being less counter-intuitive.

#### Jack Daniel

##### dice-universe.blogspot.com
When I run basic D&D, I use an even simpler algorithm:

Roll under (enemy's AC + your Attack Bonus) and you hit. If you roll a one (an "ace"), you crit.

Works like a charm.

#### mkill

ANYTHING that requires me as DM to tell the player the monster's AC (as opposed to "you hit / miss") is a design fail.

Keep AC on the DM's side of the equation.

#### delericho

##### Legend
Target 20 isn't a bad system, but it has two very important constraints:

- The AC must always be positive. That's fine for OD&D, but even as early as 1st Ed it is no longer true.

- The DM must be willing to tell the players the AC of their targets, even if there is some hidden defence that by rights they should not know about.

If either of these constraints are broken, Target 20 requires either that players perform a subtraction, or that they handle negative numbers. Neither of these is inherently bad... but they negate the benefits of the system and give the win to the 3e/4e model.

Even with those constraints in place, the 3e/4e model feels more intuitively right - it makes more sense that a harder task has a higher target number, rather than that it gives you a smaller bonus on the roll.

#### Blacky the Blackball

##### First Post
I'm a big fan of the "Target 20" mechanic.

I came up with it independently when writing the second printing of my Dark Dungeons retro-clone of the BECMI/RC rules, and I use it there instead of using an attack table or THAC0.

During playtesting with 7-13 year old kids, I found that they easily understood the Target 20 mechanic but struggled with the more varied mechanics for other systems which still used a variety of dice and which sometimes used roll-under and sometimes roll-over.

That's what led me to write Darker Dungeons - which takes the same mechanics that Dark Dungeons has and changes them all (skills, saving throws, turn undead, and so forth) to use the "Target 20" mechanic while keeping the probabilities of success the same (within +/-5%).

#### Ratskinner

ANYTHING that requires me as DM to tell the player the monster's AC (as opposed to "you hit / miss") is a design fail.

Keep AC on the DM's side of the equation.

I dunno, my players usually figured it out after about 3 swings. I've given up worrying about it. I haven't noticed that it really changes anything but to make combat run more quickly by letting the fighter types figure out what they need to roll. I used to keep enemy hit point secret, too, but nowadays just put %ile dice next to them after they are wounded.

#### Ratskinner

I like the mechanic personally, and I think it works for non-combat as well. That is, DCs run from Super Easy 10 to Super Hard -10, with 0 being bog standard. While I realize that ascending AC is somewhat intuitive, using Target 20 is also intuitive so long as you envision it as a penalty on the attacker's roll, not an inherent quality of the character.

Unfortunately, I do seem to recall that 2e best AC was actually -22 or something like that, once you tacked on all possible bonuses. (At least as best as my friends and I could figure.) However, that required a bunch of buffs like Invisibility and quite unlikely stats and magic items, IIRC. So maybe the ranges should be adapted, or maybe not. I suppose that would depend on the design of the new system (stacking rules for one easy example.)

All that being said, while I would support such a rule, I'm not holding my breath for it. For whatever reason, too many people find minus signs scary.

#### Charwoman Gene

Target 20 isn't a bad system, but it has two very important constraints:

- The AC must always be positive. That's fine for OD&D, but even as early as 1st Ed it is no longer true.

I weep for whoever tried to teach you integer arithmetic.

#### delericho

##### Legend
I weep for whoever tried to teach you integer arithmetic.

If you had read the rest of my post, you would have seen the paragraph where I talk about what happens when those constraints don't hold - specifically that the algorithms work, but you don't get the benefits that Target 20 claims to offer.

#### nightwalker450

##### First Post
If this is serious, then I guess they're giving up on speeding up combat. Between this and opposed checks for spells, you've got a ridiculous amount of rolls/hunting for numbers that is completely unnecessary.

Or, maybe that's why we're looking so much at SoD, because if we can reduce combat to a single round of unnecessary rolls and hunting for numbers than it's quicker!

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#### WheresMyD20

##### First Post
asically, it is "Roll d20 + attack bonus + AC". You always hit on a 20 or higher, or miss on a 19 or lower. (This is based on the era when lower AC was better). Attack bonus was defined as level for a fighter, 2/3 level for a cleric, 1/2 level for a wizard.

So it's
d20 + attack bonus + AC >= 20
Subtract AC from both sides and you get
d20 + attack bonus >= 20 - AC

Why not just subtract AC from 20 and record that as the number needed to hit you? For example, if your AC is 4, then you're hit on a 16 or better. Attacks simply become d20 + attack bonus vs. number needed to hit. Attack rolls are simpler and AC stays on the DM side of the equation.

#### mkill

So it's
d20 + attack bonus + AC >= 20
Subtract AC from both sides and you get
d20 + attack bonus >= 20 - AC

Why not just subtract AC from 20 and record that as the number needed to hit you? For example, if your AC is 4, then you're hit on a 16 or better. Attacks simply become d20 + attack bonus vs. number needed to hit. Attack rolls are simpler and AC stays on the DM side of the equation.
Because that's D20 system/3E/4E. Because obfuscating simple equations by elementary school arithmetics is old school. (*)

(*) While this is not representative for players who just like older editions, I've seriously seen someone claim that THAC0 was a watershed between people smart enough to play D&D and the hoi polloi.

Now stop stepping on everyone's lawn.

/sarcasm

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