Why THAC0 Rocks

[I'm A Banana]

I hear Time Cube is easy to explain, too.

THAC0 is counter-intuitive. I roll a dice, and I know if I hit AC0, but unless the monster has an AC of 0, I still have to do math to find out of this particular monster is hit.

AC vs. BAB is more intuitive. I roll a dice, and I know if I beat a number. All the math I do applies to the die roll itself, rather than to an abstract number on a chart.

It's more of a psychological thing than a rational thing, but games are all about psychology, so....

Of course, you might like THAC0 and think it rocks. BAB, I think, tends to work better for more people than THAC0 does. But don't let my opinion stop you from rocking out however you want...D&D's lovely for that most of the time.

 

[Mercutio01]

I never understood THAC0 as a mathematical function. In fact, until I saw it plainly written here, I don't think I would ever have been able to explain it. I used to just use a little line table on my character sheet with the ACs ranging from -X to +X. Underneath I would write the THAC0s, as below.

-2 -1 0 +1 +2 +3 +4 +5
22 21 20 19 18 17 16 15

When I'd roll, I would just look at my mini chart and tell the DM what AC I hit.

For me, rolling a d20 and adding my bonus and then telling the DM what I hit was infinitely easier. It was by far THE systemic alteration that made me switch from 2E to 3E

 

[Ariosto]

"Six of one, half a dozen of another." The Monster and Treasure Assortments included "THAC9," as I recall.

Now, one nifty trick with a "roll-under" approach is to avoid subtraction by calling for a roll over a penalty.

 

[kenmarable]

I have no problem with people who prefer THAC0, but for me personally, that was one aspect I was very happy to see replaced. Re-done saves for 3.0 were also great. Sure, with both THAC0 and BAB, the math is easy for a elementary school kid, but overall, there were some really unnecessary complexities.

Having new players not have to draw little up or down arrows next to all their numbers in order to remember which ones were "high number = good" and which were "high number = bad" is bonus in my book. ("I have a strength of 18/70%, save vs. Rod, Staff, Wands of 6, 65% pick locks, and AC of -2.") I played so long, it was all intuitive. But I introduced a lot of players to the game during 2e, and the most common question was always whether a high or low number was good. There was no real design consistency at all across the board.

Plus, having pretty much everything in the game (attacks, saves, skill checks, ability checks) all being "roll d20 and add you modifier, try to hit a target number" makes the game SO much better for me and the people I game with. As much as I loved all those years of OD&D, 1e, and 2e (and yes, I did really enjoy 2e), I have ZERO interest in ever playing those systems again. Nothing wrong with others who do enjoy it - they aren't bad systems. But for me personally, THAC0 is fun to look back on, but not something I ever want to think about during a game again.

 

[Chaos Disciple]

Sorry if this is a little off topic

"With THAC0 you figure out what number you need to roll on the die once. With BAB you roll the dice, add your modifier, and compare it to the target number . . . every single attack."

I agree - this does make THAC0 easier to use, where AC is known. You can do the same with ascending AC by deducting your attack bonus from the AC to get target number, but it's less intuitive.

S'mon

You used the term "target number" in two differnt ways.
First as the AC (or Defense #).
Second as the number rolled on the dice.


I believe the first one was correct. But personally I would prefer the term "target number" to refer to the number you have to roll.

Anyway
Just an observation-carry on

 

[Hussar]

There's one problem of THAC0 that hasn't been addressed.

AC in 3e or 4e is not limited to -10. You have AC's in the (if you translated) -20 or -30 range at higher levels. THAC0 suddenly becomes a lot trickier when you have +47 to hit.

Player: Hey, I have a THAC0 of -27, I roll a 14, I guess I hit an AC of minus 51. Do I hit?

The numbers in 3e and 4e are such that limiting yourself to a range of AC's from 10- -10 just doesn't work, and once you get beyond those AC's, THAC0 become much more difficult to use.

 

[Philotomy Jurament]

This is one of those things that I just can't get that worked up about. I don't have a problem with BAB. I don't have a problem with THAC0. Heck, I don't even have a problem with "look at the chart on the screen or on your character sheet." It just isn't a significant factor, for me.

That said, one thing I like about the old AC system is that it allows some cool or interesting concepts about negative AC. For example, AC0 might be considered a "break point," or "highest AC possible without magic," with negative AC being the result of magic. Dave Arneson has used a rule where negative AC represents magic AC such that you need equal positive magic to overcome it; that is, if a monster has a -2 AC, you need a +2 weapon in order to damage it.

One thing I find interesting is that in the original D&D LBBs, your PC's armor class was an actual class, and it indicated the kind of armor you wore. Dexterity doesn't modify AC, and magic armor doesn't either -- it subtracts from the enemy's "to hit" roll.

(Robert Fisher writes about some THAC0 approaches, here.)

 

[Philotomy Jurament]

The numbers in 3e and 4e are such that limiting yourself to a range of AC's from 10- -10 just doesn't work, and once you get beyond those AC's, THAC0 become much more difficult to use.

That's a good point; the numbers and scale in the WotC editions is much inflated, compared to early D&D. (I found the larger numbers involved as levels went up in 3E to be off-putting, BAB or not, but I can see how BAB would be a little easier than THAC0, in those situations.)

 

[Runestar]

THAC0's explanation always seemed a little weird to me.

The lower your AC/THAC0, the better. You want to roll high, but your final attack value must be lower than your opponent's AC for you to hit.

It is a piece of cake once you have it all figured out, but that is just a layer of confusion which was never needed in the first place. I still remember my puzzlement when in Planescape: Torment, I saw my AC decrease when I had the nameless one wear that ring of AC+2, finding that I couldn't remove it as it was cursed, and thinking "crap, did I screw up?", despite the ring's entry stating it was supposed to be a boon.

 

[Fifth Element]

I do admit that understanding how THAC0 functions is slightly more difficult conceptually. However, it more then makes up for it in accelerating game play.

I'll disagree and I'll tell you why. THACO is faster...for the players. Because it puts more of the maths on the DM. The player may only need to know what he rolled, and tell the DM, but the DM has to know both the target's AC and the attacker's THACO. Moreover, he has to know the THACOs of all the players at the table. If the players do the math on their attacks, it should be less time-consuming because they only have to worry about their own attack bonuses, as opposed to the DM needing to know the THACOs of everyone at the table. Players learn their own attack bonuses very quickly. The DM has other things to worry about than commit the party's THACOs to memory.