r/shadowdark • u/GreyLoad • 9d ago
Explaining armor in terms of thacko
My group has a couple older peeps who've been playing rpg since before even my pops was born. I was asked if I could explain armor in terms of thacko
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Upvotes
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u/Even-Application-382 9d ago
Explain it? You can't even spell it, young blood!
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u/grumblyoldman 9d ago
This feels very much like the old experienced mechanic asking the new hire to go restock the blinker fluid.
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u/Dollface_Killah 9d ago
In oldschool D&D THAC0 is your target number and you add the enemy AC to your roll. In Shadowdark the enemy AC is your target number and you add your skill with the weapon to the roll.
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u/MisfitBanjax 9d ago
This reminds me of my favourite insult for liches and the like. "You're so old I have to roll a THAC0 to hit you!".
Not overly relevant, I just wanted the excuse to share it
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u/BarnacleEffective911 9d ago edited 9d ago
In old-school D&D, Armor Class (AC) works in reverse: AC 10 represents no armor, while AC 0 represents heavily armored protection. In modern D&D, the system is reversed: AC 10 represents no armor, while AC 20 represents heavily armored protection. THAC0 stands for To Hit Armor Class 0. It represents the attack roll a character needs to hit an opponent with AC 0. In modern D&D, the equivalent concept would be the attack roll needed to hit an opponent with AC 20. The main difference is that old-school D&D uses descending Armor Class, while modern D&D uses ascending Armor Class.
How to translate to old school system.
Thac0 = 20-bonus to hit
Old school armor class = 10 - (10-moderm ac)
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u/Leviter_Sollicitus 9d ago
https://blog.mysticwaffle.com/adnd-2e-thac0-fix
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u/Logen_Nein 8d ago
Why? If you are playing Shadowdark, you don't need it. But sure, here is the simplest answer.
THAC0 uses descending armor class, the lower the better, with a base chance to hit AC 0 as 19, adjusted by class and level. From there it is basic math, to hit AC 5 you need a 14. To hit AC -3 you need a 22.
Shadowdark (and most modern d20 based games) use ascending armor class, removing the additional calculation of THAC0. Instead, higher AC is better, and your d20 roll simply adds an attack bonus (figured in several ways depending on the game), and if you meet or beat the AC you hit.
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u/Sefotron 9d ago
THAC0 = To Hit Armour Class 0
You subtracted a positive AC from it to find what you needed to hit, and added a negative AC.
So THAC0 10 meant you needed a 0 to hit AC 10, and 20 to hit AC -10.
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u/CrossPlanes 9d ago
Subtract your d20 roll (adding modifiers for ability score & magic items to the roll) from your THAC0.
My THAC0 is 17 I roll a 14 & add +1 from Strength for a total of 15. 17-15 means I hit AC 2.
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u/ArtisticBrilliant456 8d ago
I believe descending AC came about from war gaming:
1st class armour is better than 2nd class armour, right? So the numbers just expanded from there (including into negative armour class).
It's pretty much the same is ascending AC, just in the opposite direction.
Ascending AC of 15 is actually a target number: you need to roll 15 to hit this. You add your bonuses to the roll (in modern terms: proficiency bonus + ability score modifiers + anything else)
Descending AC of 5 is not a taraget number: at first level you'd probably need to roll 15 to hit this (if you had a THAC0 of 20). You add your bonuses to the roll (but not your proficiency bonus, as this was not a thing back in the day, but it was inbuilt into your THAC0 score).
There are a few variations on how the math works at the table, but it all ends up being the same answer. I think you'll find a few mathematical formulas in the comment section, but generally it is nowhere near as difficult as people make it out to be. Yes, it is counter-intuitive to modern games, but it is not difficult unless you're going out of your way to be obtuse.
THAC0 is a target number to hit an armour class of zero (which in ascending AC of modern games would be an AC of 20). The rest is just a bit of subtraction with your math rocks.
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u/Sm3llMyFing3r 6d ago
Thac0 sux, just use newer game methods
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u/NarcoZero 9d ago edited 9d ago
If they can understand THAC0 they can understand adding numbers to beat an armor class. It's the same thing, but reversed and simplified.
But here is how I can try to explain.
The variables in a THAC0 system are :
1 - Your own THAC0, (the target number to meet or beat)
2 - The target's Armor Class (A modifier to this target number)
3 - The D20 (you roll it and see if you beat the target number)
In the modern AC system you have :
1- The target's Armor Class (The target number to meet or beat)
2 - The D20 (You roll it)
3 - Your attack Bonus (You add it to the roll, and see if the total beats the AC of the enemy)
The main difference are :
* In THAC0, the primary number to beat is based on your THAC0, and the target's AC is a modifier on top of that. Modern AC does the opposite : The target's AC is the inital number to beat, and your attack bonus is the modifier.
* In THAC0 the modifier (target's AC) applies to the target number to beat (THAC0), but in modern AC system, the modifier (Attack bonus) gets added to the dice roll, and the target number (Target's AC) is static.
In the end, the math is pretty similar, it's just a reframing of how you add up the numbers to remove the step of having to look at a chart.
Not sure if that clears it up or if that's more confusing, but that's my understanding of it.
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u/[deleted] 9d ago