@Derp
Thac0 is awesome, and sensible.
Or the opposite of both of those things. I'm kidding about the 'or', it's just that one, the opposite of those things one.
How much AC does a suit of Chain Mail (AC 5) +3 give you? If you answered 2, congratulations, you got it in one. Because of course 5+3 is 2. Except that lower is better so the 5 is dropping you from the 10 of an unarmored human so 2 is better than 5 is better than 10 so obviously +3 really means -3. And if you're really lucky you can get to the point of having a negative value so that when figuring out your to-hit number you can subtract a negative number and...
Yeah, sensible and awesome, totally.
I realize that much of that is a factor of AC rather than of THAC0 directly, but it's part and parcel of the same subsystem so it's just as guilty.
Thac0 is just too much mathing.
If you've got an AC of -3 and a THAC0 of 12, and your enemy has an AC of 2 and a THAC0 of 15:
- Your chance of hitting them is 12 - 2 = 10, if no armor v weapon interaction.
- Their chance of hitting you is 15 - -3 = 18, if no armor v weapon interaction.
For 3.x/Pathfinder it's the same numbers, just calculated differently, with 20-(THACo or AC) to get the converted values. You'd have an AC of 23 and To-Hit of 8, they'd have an AC of 18 and To-Hit of 5.
The difference being that there's not stupid shit like listing positive modifiers to represent negative values, or subtracting negatives. A + is a + and a - is a -. Positives are good to have, negatives are bad to have, period.
THAC0 offers absolutely nothing over the 3.x model except a less intuitive system, and slightly worse to-hit numbers for non-warrior classes. That's not exactly hitting 'sensible and awesome' for me, I guess.
Who knew that as you progressed in level, you would get harder to hit by dint of being a combat veteran? No, fighters and such remain just as hittable forever, better have nicer armor
Err. Okay, it's been a loooong time since I played AD&D, but I don't remember getting AC bonuses by level. 10 was unarmored human, modified from there by armor. So an unarmored fighter and an unarmored wizard with the same exact Dexterity both had the same AC.
Am I misremembering this? It's possible.
tl;dr - You're both monsters.