DH's Blog
Math
One of the few things from the new school that I like to keep in my old school games is ascending armor classes. I think it's much easier to deal with than attack matrices or THAC0 or the like. Anyway, I've posted about this before, I even wrote a pdf detailing a system for such.
Anyway, I used this system when I ran my B/X oneshot a while back, and while explaining that the conversion from old AC to new AC was 10 + (10  AC), Delta quickly pointed out 'or just 20  AC'. Um, yeah, the associative law, of course. You can even see that formula in the pdf linked above though. Though, I find it interesting that my mind didn't go there. I think it's because I still find it easier to think of inverting a single digit number and then adding a tens digit than subtracting from 20. I wonder if that isn't why they used the descending AC system to start with? An AC in the range of 110 is much easier to deal with than one in the 1020 range. Though, this of course doesn't take into consideration negative ACs in the descending system. I've recently been playing All Flesh Must Be Eaten with my current group, which is based on the Unisystem. This system is d10 based, with stats and skills all in the 15 range. Rolls are simply d10 plus the stat and the skill. Though there's no AC in this system, so the comparison breaks there. Still, there's something attractive about all the low numbers here. On the other hand, a d10 based system means all probabilities are in increments of 10%, while a d20 based system is in increments of 5%, and I think the latter is preferable. I don't much to back that assertion, simply that 5% increments feels like the right granularity. I've played pure percentile systems (eg. Warhammer), and a 1% change is really pretty imperceptible at the table. A +1 on a d20 though is noticeable, and +1 on a d10 is a big change. I'm not sure where I'm going with this, I have no conclusions here. Just some interesting things I've been noticing about the games I play these days.
