So a friend of mine wants to run an oldskool ADnD 2nd edition game. I am trying to get a handle on the rules...

So a friend of mine wants to run an oldskool ADnD 2nd edition game. I am trying to get a handle on the rules. How does THAC0 work?

First level. Thac0 is 20. Roll d20 to hit. Count UP from the number you rolled to 20. That is the AC you hit.

Each level you might have to change that number based on class. Worry about that later.

Same with magical weapons. Worry about it later, just get your head round the basics. Not difficult.

It's basically just the inversion of the system as you know. You subtract AC to it to find the TN. So THACO 15 and AC 9? You need 6 or more to hit.

THAC0 stands for "To Hit Armor Class 0". Make your attack roll, and add the target's armor class to it. If the sum is greater than or equal to your THAC0, it's a hit.

Example
>first level
Roll 15 on d20
>hit AC 5

>Third level fighter
Thac0 18
>roll 15 on d20
Hit AC 3
Etc etc

Is THAC0 "good?" Because I've seen even the Retroclones replace this system.

It's a little non-intuitive to new players. Not inherently bad.

Die roll - THAC0 = AC you can hit.

THAC0 differs by class and level but your DM should just tell you it.

It isn't "bad", It's just difficult to explain to retards, most systems that replace it are functionally identical.

OP the basic rule is: :THAC0 − AC = roll needed to hit.

So Lets take the example of a Generic Adventurer and Magical Training Dummy.

The Adventurer has THAC0 20, AC -1. The Magical Training Dummy has THAC0 15, AC 10.

The Adventurer attacks the dummy. He Checks his THAC0 (20) and Subtracts the AC of the Dummy (10). Plugging in the numbers to the rule we get: 20-10 = 10. The adventurer needs a roll a total of 10 or more on the D20 hit roll to hit the Dummy.

The Dummy then attacks the Adventurer. He checks using his numbers. In this case THAC0 (15) vs AC (-1). Plug in the numbers to the rule and we get: 15 - (-1) = 16. For simplicity, and because some people don't understand negative negatives, treat all "negative armour classes" as positives: So 15+1 = 16. The dummy needs to roll a 16 or more to hit the adventurer.

Attack Roll - THAC0 = AC hit

The way I do it is THAC0 is the target number and AC is a modifier I add or subtract to the roll.

This. Once you grasp that higher AC in 2e is BAD, instead of GOOD, THAC0 is actually... Okay well it's not intuitive but it isn't hard.

Still overcomplicated, tho.

Imagine i say "you have to substract your base attack modifier from your target's ac to get the number you are going to roll, then you add your attribute bonus to your roll!" (Ascending ac as explained by someone bad at explaining)

THAC0 is just the same system still in use with a substraction in there somewhere. It's quite literally the same system and math.

LOL'ed more than I should. It is exactly that: bad explanation.

THAC0 = To Hit Armor Class 0

Let's say your THAC0, like all first-level THAC0's, is 20. That means you roll against someone with AC 0, you hit on a 20.

Now let's say you're fighting someone more reasonable, with an AC like 9. You subtract 9 from 20, getting 11: you need to roll at least an 11 to hit this target.

High AC means easy mark in pre-3E D&D.

Its needlessly confusing.

What if THAC0 was shortened to "Accuracy"

So for reference I started with 3.0, prefer low-maths systems etc. I have no idea how THAC0 is confusing. It's the same thing as AC as a flat number but then modifying the attack roll, just a slight transposition of operations and subtraction instead of addition. The part that makes post-THAC0 attack/defense simpler is just that all of one PC's attack rolls are modified mostly in the same way, so while the math is done in the same number of steps it doesn't need to be re-checked against each target.

It's not bad, it's just that nuDnD attack system involves easier to understand linear number progression, that's all.

and by weapon vs certain armours.

don't forget stuff like chain has a higher ac against slashing, but less against crushing and piercing.

LOWER* ac against slashing and higher against crushing and piercing*

This is a simpler explanation with no negative negatives:

>Still overcomplicated, tho.

Math is hard. Let's go shopping!

>print out incredibly autistic tables that give out small bonuses and penalties for using certain weapons against certain types of armor
>let attack bonus scale with level but leave the AC a fixed number
D&D.

Oh, i know! Add your opponent's AC and any bonuses to your roll, then compare to your THAC0. There.

THAC0 is "To Hit Armor Class 0". So, if you have a THAC0 of 0, then you need to roll at least 0 (or higher) on a 20-sided die to hit a monster with an armor class of 0. In other words, you'll always hit. Lower is better because you don't have to roll as high. I don't know if these rules were put into BG2, but in general 1 is a critical miss (regardless of your THAC0) and 20 is a critical hit (whether or not you could really hit the monster). Which means there's a 5% chance that you'll miss regardless of THAC0 and a 5% chance you'll hit regardless of THAC0.

So to figure out how likely you are to hit someone, you take THAC0 - AC (since a negative armor class is better).
THAC0:4 - (-2 AC) = 6
THAC0:8 - (3 AC) = 5
THAC0:-2 - (-12 AC) = 10

read the book you fucking subhuman and stop wasting our time with your shitty questions a thread died for this.

I'd rather a thread that helps explain an old system to a newer audience than any of the other bullshit that I've seen on Veeky Forums in the past few years.

If you're still having a hard time after Veeky Forums explains it (which would not surprise me - thac0 is really simple but people make it sound complicated) make yourself one of these visual aids right here, it should give you the feel of it.

Tell your friend he is stupid and just forget it. The only good thing about AD&D is the fluff/lore/content. Especially 2nd edition is stupid. I cut my teeth on AD&D, and I never looked back once anything at all else came out and was available. Don't listen to a bunch of dipshits' misguided nostalgia. Just tell your friend to fuck right off.

RTFM, ya lazy ass.

>I don't like AD&D and neither do you!

Well, okay, in this user's case you're right, but that's only because Basic is so much better without all the Gygaxian autism.

Imagine what TTRPGs would be today like if Gygax understood math...

>implying he didn't

You should read up on the dude, the stuff he did in the wargaming community was fairly impressive.
When I said Gygaxian autism I meant all the polearms and shit, and the complicated subsystems and stuff that made it "Advanced."

Actually it wasn't. You must be easily impressed.

Yeah, if you're a fucking retarded millennial

GenXer here, THAC0 is stupid.

AC with negative numbers....that's literally it

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I’ve been wanting to play AD&D again. I’m pretty young but I started playing the red box starter set when I was like 10 so that and AD&D really holds a soft spot for me. I doubt I could get my friends to play it though since they mostly started with 3e. Also there really doesn’t seem to be any good online resources for it.

Check on Roll20, there are OD&D, Basic, and AD&D games up all the time, some of them old-style open table games where players can come and go.

THAC0 is pretty much how difficult it is for you to get a meaningful hit in on someone.
d20 + Ability Score Bonus + Item/Circumstance Bonus + Target Creature's AC vs. THAC0. If it's greater than or equal, you hit.
If you have a THAC0 of 18 with a +1 sword and your target's AC is 7, you need a 10 or better to hit.

Watch this

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Hah, watch this

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You think that's cool, watch this

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d20+(Mods) >= THAC0 - enemy AC

You have to say Watch This ,and it works every time.

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It's amazing how much more they did in 70 odd pages than modern D&D does in several hundred

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watch this

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Fun fact: Ice T did voice work for some D&D audiobooks. He recounted it on his podcast as some "crazy, deep nerd shit."

>This motherfucker got a sword that talks to him and shit!

Whoa, HEY GUYS!. IS THIS THAT NEW Veeky Forums MEME I HAVE BEEN HEARING ABOUT?! GONNA HIT THAT THAC0 AHAHAHAHA

I remember it always felt backwards.

Grab her right in the THAC0

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>we need more magewank and more threads pointing out how needlessly stupid and contradictory Warhammer 40k novels are

nope. Git fucked.

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Sure thing, grandpa. Tell us some more about how awesome Rolemaster was.

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I approve of this image

>go on tg thread
>no THAC0 thread
>thread about players inventing guns in medieval fantasy games though
At least there is one archer thread

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You think Archers cool, but watch this

go away darbo

OMG, which ones? I hope it was Terror TRAX, that shit was DOPE.

>Hi ladies! I'm going to...
*(rolls dice)*
>....sexually harass you!

Please be patient I have T H A C 0,

>Watch this

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Hey Ladies

Is THAC0 of interest to the elves?

is a 10 of interest to the elves

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Are these dubs of interest to the elves

Have you heard of the High THAC0s?

Haha watch this
*rolls a one*

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>Are we posting in a thread right now

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Nice trips daddy-o, but watch this

>Whats a THAC0?

>tfw millennial and likes THAC0

He was reading for one of the short storied in Audible's The Legend of Drizz't: The Collected Stories.

>Motherfuckers talk like Yoda!


Lucky for you there's no critfails in AD&D.

*rolls for genocide*
>What's the THAC0 of a capital ship's airlocks?

>not the superior version

How much THAC0 does a forest in the high moor
have?

Good Lord! What is happening in there? - THAC0. - Uh- THAC0 at this time of year at this time of day in this part of the High Moors localized entirely within your Cave? - Yes. - May I see it? No.

Not enough THACO to protect it from a molotov

Considering it can't attack anything, it doesn't have a THAC0.
Now if it were a bunch of Ents, maybe.

I want to use Double or THAC0

>me playing a wizard in 2e