Thac0?

[Greylond]

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[Knaight]

But in general, what I found confusing about the Thac0 stuff was not Thac0 itself, but just the instinctive reaction of what modifiers were good.

-1 hit? Bad
-1 AC? Good
-1 Thac0 (definitely present in various games that used 2e rules, not sure if it was used in actual ADnD materials)? Good...I think...wait, are negatives supposed to be a penalty?

Then there's things like a magical +1 bonus to armor gives -1 AC.

Yeah, this is just bad design. There are, for an arbitrary reason that doesn't actually help anything, way more points of data that need to be memorized to do the same thing. The core concept of BAB vs. AC, and the whole concept of d20+modifiers heavily streamlined everything.

Of course, the concept of dSomething+modifiers vs. difficulty has been around for a long while, certainly well before 3.5, so its not as if this simplification is actually impressive.

[Matthew]

Yeah, this is just bad design. There are, for an arbitrary reason that doesn't actually help anything, way more points of data that need to be memorized to do the same thing. The core concept of BAB vs. AC, and the whole concept of d20+modifiers heavily streamlined everything.

Of course, the concept of dSomething+modifiers vs. difficulty has been around for a long while, certainly well before 3.5, so its not as if this simplification is actually impressive.

It is actually bad development of the design. Instead of saying "+1 to hit" or "opponent's have −1 to hit you" the modifiers were applied to AC or THAC0 as though they were generalised "attack" and "defence" values, which was not the purpose of the initial design.

[Toofey]

I just dont understand why it isn't explained as: You subtract your roll from your thac0 to see what AC you hit. But it's a counterintuitive mechanic whatever way you slice it.

[Talakeal]

If it really confuses you, you could always just reverse it, 20 - thaco = base attack, so a thaco of 17 is a +3 base attack bonus. Then you just reverse AC so it ranges from 10-30 instead of -10-10. The 4AC from our example above would become a 16 then.

Which is of course what they did for 3.0.

[The Big Dice]

I just dont understand why it isn't explained as: You subtract your roll from your thac0 to see what AC you hit. But it's a counterintuitive mechanic whatever way you slice it.

It's no more counter intuitive than any other mechanic. And it's actually less prone to clutter than the modern D20 conventions. There's less sources of modifiers to keep track of for one thing. And certainly in D&D and possibly 1st edition AD&D, there's a handy chart to consult to see what your roll results in.

The idea behind THAC0 being, that was the formula used to derive the chart.

[hamlet]

The idea behind THAC0 being, that was the formula used to derive the chart.

Except that the original chart wasn't a direct linear progression once you got to the far ends of the Bell Curve. But, yeah, in general it was the formula that generated the chart. Personally, I preferred the chart in some instances.

And as for intuitiveness, it's not "counter intuitive." It's just not intuitive to you. It's also poorly explained, but that's a matter of editing. Take the modified roll, add the AC, and if it equals or exceeds THAC0, it's a hit. If not, a miss. That's not very difficult. It's just a target number where half the calculation is secret from the player.

[The Big Dice]

Except that the original chart wasn't a direct linear progression once you got to the far ends of the Bell Curve. But, yeah, in general it was the formula that generated the chart. Personally, I preferred the chart in some instances.

There's no bell curve in D&D. The 1st ed DMG went on at great length (on page 1 at that) about this. A 20 sided dice only generates a linear probability spread. And the D&D charts (as opposed to the AD&D ones) were strictly based on the formula of Thac0 -AC = required number on a D20 to hit the target.

And as for intuitiveness, it's not "counter intuitive." It's just not intuitive to you. It's also poorly explained, but that's a matter of editing. Take the modified roll, add the AC, and if it equals or exceeds THAC0, it's a hit. If not, a miss. That's not very difficult. It's just a target number where half the calculation is secret from the player.

I used to resolve that by asking people to tell me what AC they hit. And if you tell them that the orc is wearing chain and carrying a shield, they'll probably have a ballpark AC in mind anyway.

[Greylond]

Except that the original chart wasn't a direct linear progression once you got to the far ends of the Bell Curve. But, yeah, in general it was the formula that generated the chart. Personally, I preferred the chart in some instances.

Actually, for Fighters it was. The chart only had every other level shown but if you looked at the Charts notes it said for Even levels to add a +1...

[spaceLem]

It's no more counter intuitive than any other mechanic. And it's actually less prone to clutter than the modern D20 conventions. There's less sources of modifiers to keep track of for one thing. And certainly in D&D and possibly 1st edition AD&D, there's a handy chart to consult to see what your roll results in.

The idea behind THAC0 being, that was the formula used to derive the chart.

It has already been pointed out that the number of modifiers and which direction AC and attacks go are entirely unrelated. 3e being complicated has no bearing on how good or bad THAC0 is.

I think some ways of handling THAC0 are better than others. The way I learnt (THAC0 - d20 = AC hit) is probably my least favourite. If your GM is nice enough to tell you the enemy's AC, then roll d20 + AC and beat THAC0 is good (making it into a simple DC).

There are various combinations of attack bonus or THAC0, ascending or descending AC, and how to handles them. Some are definitely easier or quicker than others, but these are not necessarily the same as most intuitive.

[The Big Dice]

It has already been pointed out that the number of modifiers and which direction AC and attacks go are entirely unrelated. 3e being complicated has no bearing on how good or bad THAC0 is.

Less clutter, less things to forget about and less complications when filling in a sheet. That makes THAC0 objectively less complex. Which makes me think that people arguing against it are arguing from a position of never having played the games that used it. And used it with minimal problems for the best part of three decades.

I think some ways of handling THAC0 are better than others. The way I learnt (THAC0 - d20 = AC hit) is probably my least favourite. If your GM is nice enough to tell you the enemy's AC, then roll d20 + AC and beat THAC0 is good (making it into a simple DC).

Or you tell the GM what AC you hit and he tells you if the attack succeeded. You don't need to know the enemy AC in advance to be able to know what you hit. In fact, that's exactly what you're doing in modern D20 games. Rolling, adding modifiers, tell the GM what AC you hit. You can paint it any colour you like, but that's the process.

There are various combinations of attack bonus or THAC0, ascending or descending AC, and how to handles them. Some are definitely easier or quicker than others, but these are not necessarily the same as most intuitive.

Here's a fact: if you've played a game system for a while, it gets to the point where you can work out relevant calculations in your head, without being prompted and fairly quickly. That's when the system becomes intuitive. Before then, it's a mathematical process that may or may not cause different people difficulty.

There's no such thing as an intuitive game system. If there was, you wouldn't have to learn how it worked.

[spaceLem]

Less clutter, less things to forget about and less complications when filling in a sheet. That makes THAC0 objectively less complex. Which makes me think that people arguing against it are arguing from a position of never having played the games that used it. And used it with minimal problems for the best part of three decades.

No, this is not true. It tells you that a system without modifiers (AD&D) is objectively less complex than a system with lots of modifiers (d20).

THAC0/dAC is not objectively less complex, it's just one way of arranging the numbers to get a desired probability, and AB/aAC is another. Which method you use is entirely irrelevant to the complexity of the underlying system, but you're tangling the two issues up here.

[Matthew]

Less clutter, less things to forget about and less complications when filling in a sheet. That makes THAC0 objectively less complex. Which makes me think that people arguing against it are arguing from a position of never having played the games that used it.

I do sometimes wonder about that. Back when I was in my early teens and playing AD&D there was no discussion about whether THAC0 was difficult or would it not be better to do it another way? It just never even crossed our minds. Only when somebody pointed out in the pages of Dragon that armour class could be ascending and THAC0 converted to a bonus to hit did it become a consideration. These systems cannot be too intuitive/counter-intuitive if the former is not considered cumbersome by the players and the latter not obvious to them as an alternative. Preference is really the key here, masquerading under the cloak of absolute values. As has been endlessly pointed out, though, the real issue with THAC0 is the language used to described modifiers, such as unqualified "−1 to AC", which is unintuitive, because of the general nomenclature of negative and positive values suggest that the former is "bad" and the latter is "good".

Anyway, for more on this topic, people might be interested in this old thread, which explains the whys and wherefores of THAC0: [AD&D] Why THAC0?

[a_humble_lich]

As has been endlessly pointed out, though, the real issue with THAC0 is the language used to described modifiers, such as unqualified "−1 to AC", which is unintuitive, because of the general nomenclature of negative and positive values suggest that the former is "bad" and the latter is "good".

In practice how bad of a problem was this? I can't remember ever being highly confused in 1st/2nd ed. wondering if the modifier should add or subtract to AC. Generally it was pritty obious. The cursed shield -1 was bad so it added to your AC, taking cover was good so the "-2 AC" made your AC lower. I agree that it was less intuitive, but do other people remember having serious problems with it?

[Matthew]

In practice how bad of a problem was this? I can't remember ever being highly confused in 1st/2nd ed. wondering if the modifier should add or subtract to AC. Generally it was pritty obious. The cursed shield -1 was bad so it added to your AC, taking cover was good so the "-2 AC" made your AC lower. I agree that it was less intuitive, but do other people remember having serious problems with it?

Almost no problem at all, since the context usually dispelled any confusion, but not always. An example would be something like a berserker rage that grants +1 to hit, +1 to damage, and −1 armour class, as it is not clear if berserker rage makes armour class better or worse.

[MeeposFire]

Another bonus to the old system was that crazy numbers were less common or not really possible. For instance an AC of 40 would not be insane in 3e (at least at some point). In 2e that would be a -20 AC. I do not recall seeing that low of a number anywhere and it would certainly be rare if you did. In 3e numbers that high or higher get very common. This can be done by the higher numbers of bonuses and continuing improvement in attack bonus that gets effectively capped in 2e (and in 1e I believe they capped AC at -10 too).

[Talakeal]

AC was capped at -10 in 2E. Which is wierd, because a level 20 fighter would still hit that on 2 assuming he had a good str and magic weapon.

I learned the game on 2nd ed, and never had a problem with it, but 3E is much simpler in that you always want to roll high and bigger numbers are always better. Its not the old way was hard, just less streamlined.

[SimperingToad]

AD&D did not have a hard cap at –10. It is certainly possible, though difficult, to go beyond. But since no one can possibly add in all modifiers, especially those granted by DM decisions, a reasonable stopping point for the sake of brevity in the books makes sense. –10 makes a nice round number. Any mildly competent DM can continue the progression without being told how.

[Killer Angel]

That said, I do like the more uniform "roll high" to succeed mechanic in later editions, though.

Yep. It wasn't difficult, but I like more the 3.x version.

How do you pronounce Thac0, by the way? Tack-zero? I know I've met people who pronounced it Taco, like the mexican food, but that's a bit weird too.

I'm one of 'em. It all depends on you mother language and the way you usually read and pronounce.

[Matthew]

AD&D did not have a hard cap at –10. It is certainly possible, though difficult, to go beyond. But since no one can possibly add in all modifiers, especially those granted by DM decisions, a reasonable stopping point for the sake of brevity in the books makes sense. –10 makes a nice round number. Any mildly competent DM can continue the progression without being told how.

It is interesting to note that second edition is inconsistent on the matter, at one point suggesting that –10 is a limit because it is the result of Full Plate +5 and a Shield +5, and at other times suggesting it is a hard limit. Given that there is no limit in first edition, I tend to agree that it was a nominal limit rather than an iron clad one. Of course, the fact that dragons can get up to –12 AC in the second edition Monster Manual is always brought up in these discussions.

[spaceLem]

On the pronounciation issue, I'd say that THAC0 rhymes with "hack-oh"

I see no reason for there to be a limit on armour class. Realistically, it's going to get more and more difficult to increase that AC, but not impossible, so there should be diminishing returns, but never a hard limit.

You could get an arbitrarily large amount of steel between you and your enemy (high armour bonus), or be so fast that the other guy couldn't even see you (high Dex or dodge bonus). Alternatively, you could be really small and get a size bonus (try hitting a greenfly in flight with a sword). Or all of these things (a really really fast midge that's invisible and protected by stupidly big armour ;)

[hamlet]

AC was capped at -10 in 2E. Which is wierd, because a level 20 fighter would still hit that on 2 assuming he had a good str and magic weapon.

By level 20, a fighter, if he'd managed to survive that long, was probably, quite literally, the best sword (or name yer weapon here) fighter in the known world for all intents and purposes. It makes no trouble assuming that, for the most part, he'd be able to hit what he's swinging at 99% of the time, barring extenuating circumstnaces such as extreme magic.

[Archwizard]

It is interesting to note that second edition is inconsistent on the matter, at one point suggesting that –10 is a limit because it is the result of Full Plate +5 and a Shield +5, and at other times suggesting it is a hard limit. Given that there is no limit in first edition, I tend to agree that it was a nominal limit rather than an iron clad one. Of course, the fact that dragons can get up to –12 AC in the second edition Monster Manual is always brought up in these discussions.

2E says that -10 is "the best" (DMG, page 51; PHB, page 89). The fact the very powerful monsters break this rule does not mean it isn't a rule. In the 4E MM, Orcus is listed as level 33, even though the maximum 4E level is 30.

On the pronounciation issue, I'd say that THAC0 rhymes with "hack-oh"

I've always pronounced it that way myself.

[spaceLem]

I've always pronounced it that way myself.

I should have said that it's also "th" as in "thorough", rather than as in "tattoo" or "then".

[Matthew]

2E says that -10 is "the best" (DMG, page 51; PHB, page 89). The fact the very powerful monsters break this rule does not mean it isn't a rule. In the 4E MM, Orcus is listed as level 33, even though the maximum 4E level is 30.

Right, and it also says 10 is the worst, but modifiers to attack rolls will effectively make armour class better or worse than 10 or −10, and it is indicated that the reason it goes from 10 to −10 is because those are the limits of actual armour ratings (from no armour to full plate +5 and shield +5). In first edition AD&D there is no limit to how good AC can get, but AC can only go above 10 as a result of cursed armour (see DMG, p. 73). Unfortunately there is frequently confusion between the two systems, even amongst the designers, which is why you end up with rules being apparently "broken" here and there.

Of course, the designers also stated at the time that second edition was never meant to replace first edition, and they expected people to mix and match between editions. "Build your own AD&D" should have been the subtitle of second edition.

[LibraryOgre]

Of course, the designers also stated at the time that second edition was never meant to replace first edition, and they expected people to mix and match between editions. "Build your own AD&D" should have been the subtitle of second edition.

"Weapon speed, I choose you!"

Really, if I were to re-introduce something from 2e to C&C, it would be weapon speeds and casting times.

[hamlet]

"Weapon speed, I choose you!"

Really, if I were to re-introduce something from 2e to C&C, it would be weapon speeds and casting times.

Yeah, I like weapon and casting speeds. Gonna be starting a new game tonight that uses them. See how it goes for a bunch of 3.xers converting up.

[Narren]

Another bonus to the old system was that crazy numbers were less common or not really possible. For instance an AC of 40 would not be insane in 3e (at least at some point). In 2e that would be a -20 AC. I do not recall seeing that low of a number anywhere and it would certainly be rare if you did. In 3e numbers that high or higher get very common. This can be done by the higher numbers of bonuses and continuing improvement in attack bonus that gets effectively capped in 2e (and in 1e I believe they capped AC at -10 too).

I notice that with stats, too. Maybe it was just my games, but none of players ended up with stats in the 20's. I think the wizard ended up with a 20 int, and the rogue ended up with a 20 dex, but they were world-renowned for it. In 3.5, that's considered a decent number at level 1.

Maybe I missed it, but am I the only one that subtracted the AC from the Thac0 and then just rolled for that number?

[Archwizard]

I notice that with stats, too. Maybe it was just my games, but none of players ended up with stats in the 20's. I think the wizard ended up with a 20 int, and the rogue ended up with a 20 dex, but they were world-renowned for it. In 3.5, that's considered a decent number at level 1.

Maybe I missed it, but am I the only one that subtracted the AC from the Thac0 and then just rolled for that number?

Yeah, I really kind of hate the stat inflation that has occurred. Pre-3E, stats above 18 were very rare and stats above 19 were almost unheard of in PCs.

I liked it that way.

And yeah, I did it the same way. "My THAC0 is 15, the target's AC is 5, so I need a 10."

[Talakeal]

AD&D did not have a hard cap at –10. It is certainly possible, though difficult, to go beyond. But since no one can possibly add in all modifiers, especially those granted by DM decisions, a reasonable stopping point for the sake of brevity in the books makes sense. –10 makes a nice round number. Any mildly competent DM can continue the progression without being told how.

The combat chapter of my second edition PHB clearly states that a -10 Armor class is the best and a 10 the worst, and I always played that you couldn't go lower.

Of course, this meant any high level fighter with a good strength and magic weapon would hit any opponent on a 2, which was really weird. It's also really weird that some dragons have -11 or -12, or that some monsters had a negative Thac0, so who knows.


Of course, none of this is as weird as the note about the Tarasque's negative Thac0 in the 2E Monster Manual, which reads "creatures with a negative thac0 can only be hit on a 1".


I think what they meant to say is that even with a negative Thac0 you still miss on a roll of a natural 1, but that is certainly not what they wrote, and trying to play RAW with that rule will result in divide by zero style total existence failure.