Harg Harfardarssen
Cipher
Thac0 is the way it is to make it less complex, not more.
I admit, though, that the solution they went with in 3rd edition is even more elegant and intuitive and removes the need for subtraction.
Yeah, I thought Thac0 was intuitive and elegant!
So you have a Thac0 of 18 and this monster has an AC of 7. 18 - 7 = 11, so you need to roll 11 to hit. Simple and elegant. But addition is even easier than subtraction so I will admit that the 3rd ed is more accessible. Still, it really isn't hard to figure out.
Thac0 - AC = roll you need to make. Very simple and straightforward, don't you agree? It's not much harder or less elegant than 3rd ed, which is
AC - AB = roll you need to make. ... come to think of it, that's still subtraction...
Now that I think about it, explain to me how Thac0 was more complex when it's as simple as I described.
Or add AB to the attack roll. If AB + AR >= AC, profit. In 2e, If AR + AC >= THAC0, profit.
THAC0 was weird because it used 0 as a midpoint, so you would have to deal with positive and negative values rather than just one or the other. Not hard, but still an extra bit of unnecessary thought (OK, so I subtract[or add] this number. Is it negative or positive? Its negative, so I'm substracting [or adding] a negative...which is adding a positive [or negative]!). Plus articulating your attack value as the roll you needed to hit a hypothetical armor class (which will change with every target), rather than a value that is constant for all attacks is a bit counterintuitive.