Let's Talk About THAC0

I'll repeat what I said earlier, because apparently it's been ignored judging by the many posts since. It's not that subtracting is harder than adding. It's that the difference is incredibly minor that it shouldn't have any measurable effect on length or difficulty of resolving combat. You're not being asked to factor polynomials here folks. You're being asked to subtract from no more than 20. That's first grade stuff. If you have a difficult time calculating "I rolled a 14, my THAC0 is 18, so I hit AC 4", then I suspect you're having difficulty with every mechanical aspect of the game. I mean, you're constantly doing harder math every time you gain or spend coins (gp, sp, etc).

Sacrosanct said:

I'll repeat what I said earlier, because apparently it's been ignored judging by the many posts since. It's not that subtracting is harder than adding. It's that the difference is incredibly minor that it shouldn't have any measurable effect on length or difficulty of resolving combat. You're not being asked to factor polynomials here folks. You're being asked to subtract from no more than 20. That's first grade stuff. If you have a difficult time calculating "I rolled a 14, my THAC0 is 18, so I hit AC 4",

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Yeah, but, why should I bother with all this new-fangled Thack-hoe stuff, when I have the attack matrices right here on my handy-dandy DM screen?

Umbran said:

Standing by un-measurable assertions is easy. It still looks like standing by your 1974 Ford Pinto* as a great car.
*Which had a reputation for blowing up if it got rear-ended

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I think his assertion in this analogy would be that his cherry Ford Pinto is not nearly as dangerous a car as it was made out to be. And he'd be right - very few Pintos actually exploded.

Sacrosanct said:

If you're gonna use an analogy, use a correct one. D&D was one of the best RPGs back then, so you have to use a good car...

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True, in 1974, it was the only RPG. If D&D was a Ford by analogy, it'd be a Model T, for certain. And the Model T remains one of the best-selling cars in history.

So I totally get standing by your Model T. Or Model A. You own a piece of history.

So, to actually add something to this discussion, while addition may be easier for more people than subtraction, and higher AC being better may be more intuitive, THAC0 does have one major advantage over BAB: With THAC0, you do the math to figure out what your target number is before you roll, so you immediately know if you hit or miss as soon as the die stops rolling. This as opposed to BAB where you roll first, add your modifiers, and then compare the total to the target number.

Both probably take about the same amount of time and effort, but by front-loading the math, THAC0 makes resolving an attack a miniature dramatic tension arc. You start from the lowest point of tension as you figure out the number you need on the die, then get a little rise of excitement as you roll the die around in your hand, the anticipation as you let it roll onto the table, coming to a climax just before the die stops rolling, and then immediate release as you see the result and know instantly if it is high enough or not. With BAB, that arc gets disrupted by having to add your modifier to the roll result in between the climax and the denouement, which while brief, does make the overall experience less viscerally satisfying. It’s a small thing, but I suspect it’s a big part of why the folks who loved THAC0 miss it, even if not consciously.

What I would like to see is a system that combined the strengths of both approaches. I already tell my players the DC of a check when I call for one to be made, perhaps it would be best to go a step further. Instead of a positive modifier to the roll, give the players a negative modifier to the target number. Sure, then you’re back to subtraction instead of addition, but I suspect it would still be more intuitive than THAC0 due to higher AC still being better, and “subtract your modifier from the target’s AC” being a cleaner way of presenting the same math than “subtract the target’s AC from a number derived from your class and level.”

For me THACO always made me pause to figure out the math every single time especially with switching gears for where the magic/strength/specialization bonus goes into the equation.

So THACO minus AC compare to roll as modified by bonuses.

"I've got a THACO of 17, I have a +2 to hit, I rolled an 11 so I hit an AC of . . . 4?" It was a little speed bump every time.

And I'd have players asking does a 12 hit? So I'd ask for their THACO and their bonuses then plug in the roll and the monster's AC to figure it out and. It was annoying.

"I've got a BAB of +3 with a +2 bonus and I rolled an 11 so I hit an AC of 16" Was quicker and less shifting of mental gears so in play it went faster and kept me more in the narrative flow of a combat and less in calculating the numbers mechanics.

I was excited when I saw it in 2e Dragon Fist and was glad it was in 3e and everything since.

*Deleted by user*

Charlaquin said:

So, to actually add something to this discussion, while addition may be easier for more people than subtraction, and higher AC being better may be more intuitive, THAC0 does have one major advantage over BAB: With THAC0, you do the math to figure out what your target number is before you roll, so you immediately know if you hit or miss as soon as the die stops rolling. This as opposed to BAB where you roll first, add your modifiers, and then compare the total to the target number.

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Why would you know your target number before you roll with THAC0? Is the DM telling you your opponent's AC?

billd91 said:

Why would you know your target number before you roll with THAC0? Is the DM telling you your opponent's AC?

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Did you do it differently? I guess I never considered the possibility that the DM might just ask you to roll and tell him the number you got and your THAC0, do the math himself, and tell you if you hit or not. That sounds awful, it’s no wonder it developed such a bad reputation if folks were doing it that way.

I never thought THAC0 was bad, or realized anyone else did, until I started hearing people complain about it on the Internet years later.

There's more historical revisionism going on here than a typical grade school U.S. History class.

THAC0 was awful. Negative AC was awful and un-intuitive. We only put up with it because we didn't know any better.

Now we do.

I never had any problems with THAC0 nor did any of my regular groups, at least to the best of my recollection. I always did the initial calculations for my characters weapons ahead of time and noted it on my character sheet. What I did really like about the THAC0 system was the immense sense of satisfaction when you finally got a fighter down to a negative AC. Then you were in business. I guess getting over 20 might feel like that to someone who never played with THAC0? I don't know, the current system, as much as it makes sense, and is elegant design-wise comparatively, still doesn't "feel like D&D" to me.